Recording and/or playback device

ABSTRACT

A disk recorder/player ( 1 ) including a skew adjusting means of a thin design is provided which includes a base ( 101 ), a disk rotation driving mechanism ( 102 ) for an optical disk ( 4 ), an optical pickup ( 103 ), first and second guide shafts ( 105, 106 ) to support the optical pickup ( 103 ) at opposite ends of the latter, an optical pickup moving means ( 104 ) guided by the first and second guide shafts ( 105, 106 ) in moving the optical pickup ( 103 ) radially of the optical disk ( 4 ), an elastic member ( 126 ) put in contact with the first and second guide shafts ( 105, 106 ) to force the first and second guide shafts ( 105, 106 ) in a direction generally perpendicular to the main side of the optical disk ( 4 ), an adjusting screw ( 127 ) put into contact with the first and second guide shafts ( 105, 106 ) from the opposite side of the elastic member ( 126 ) to move the first and second guide shafts ( 105, 106 ) in a direction opposite to the direction of forcing by the elastic member ( 126 ), and a skew adjusting means ( 109 ) which adjusts a skew, if any, by adjusting the inclination of the first and second guide shafts ( 105, 106 ) by the adjusting screw ( 127 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of Ser. No.10/761,366 filed Jan. 22, 2004, the entire contents of which areincorporated herein by reference. This application claims the priorityof the Japanese Patent Application No. P2003-025239 filed on Jan. 31,2003 and No. P2003-415741 filed on Dec. 12, 2003, the entirety of whichis incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a device for recording and/orplayback of information signal to and/or from a disk-shaped recordingmedium, and more particularly to a pickup moving mechanism which movesan optical pickup unit.

2. Description of the Related Art

Some of the recent functionally improved portable electronics such as anotebook computer or the like have a CD-R/RW or DVD-ROM drive installedtherein. With such a functional improvement of the portable electronics,it is demanded for these CR-R/RW and DVD-ROM drives to be able to writeor read data at an improved speed or for the DVD-ROM drive to rewritedata to a DVD.

The notebook computer of a small size (B-5 size, for example) can becarried more easily and conveniently than a larger-size one (A-4 size,for example). Therefore, the notebook computer is of smaller thicknessand weight while it is functionally improved. It is also demanded thatthe CD-R/RW or DVD-ROM drive used in the notebook computer should bedesigned as thin as possible.

An example of the conventional disk drives for recording or playing backdata to or from CD-R/RW and DVD-ROM is schematically illustrated inFIG. 1. As shown, a disk drive of this type, generally indicated with areference number 300, includes a body 301, a disk tray 303 providedmovably between two positions, outer and inner, and having a concavityin which an optical disk 302 such as DVD or the like is to be received,and an optical pickup unit 304 housed from the rear side of the disktray 303 and which reads information signals from the optical disk 302set on the disk tray 303.

FIG. 2 shows the body 301 of the disk drive 300, not showing the upperhalf of the device body 301. The device body 301 is composed of a pairof halves, upper and lower, which are butt-joined to each other. Thelower half indicated with a reference number 307 is open at the frontend 307 a thereof for movement of the disk tray 303, and a guide member308 provided along each of mutually opposed lateral edges 307 b and 307c thereof to guide the movement of the disk tray 303. The lower half 307has disposed at the rear end 307 d thereof a printed wiring board 309formed from a so-called rigid substrate having formed thereon variouscircuit patterns on which there are electronic parts such as a connectorfor connection to a host apparatus and the like. The printed wiringboard 309 has connected thereto an FPC (flexible printed circuit) 310for connection to the optical pickup unit 304 housed in the disk tray303.

As shown in FIGS. 3 and 4, the optical pickup unit 304 includes aniron-made base chassis 315 as a body of thereof and having a disk tableassembly 313 provided thereon, a pair of guide rails 316 installed tothe base chassis 315, a pickup base 317 having provided thereon anobjective lens 312 whose movement is guided by the guide shafts 316, anda pickup moving mechanism 318 which moves the pickup base 317 on andalong the guide shafts 316.

A cover member 320 is fixed with a binding screw or the like at a sidethe optical pickup unit 304 where the optical disk 302 is to be placed.The cover member 320 has formed therein an opening 321 through which theobjective lens 312 and disk table 313 included in the optical pickupunit 304 are exposed. The cover member 320 is formed from aluminum (Al),for example. It should be noted that the optical pickup unit 304 has ametallic bottom plate 322 provided on the bottom thereof. The bottomplate 322 is fixed with a binding screw to a compartment 325 of the disktray 303. The optical pickup unit 304 is held between the bottom plate322 and disk tray 303.

The above base chassis 315 includes an iron-made frame 327. The frame327 is shaped to have a generally rectangular form. It has formedtherein an opening 328 through which the objective lens 312 on thepickup base 317 faces directly the signal recording surface of theoptical disk 302. The opening 328 is shaped to have a generallyrectangular form in which the pickup moving mechanism 318 to move thepickup base 317, pair of guide shafts 316 and the pickup base 317supported on the guide shafts 316 are disposed. Also, the opening 328 isextended at one longitudinal end thereof a generally circular cut 329 inwhich there are disposed the circular disk table 313 on which theoptical disc 302 is placed and a spindle motor (not shown) which rotatesthe disk table 313. It should be noted that the base chassis 315 hasfixed thereto a rigid substrate (not shown) having a connector 354 forconnection of one end of the FPC 310 for connection of the printedwiring board 309 disposed in the body 301 of the disk drive 300 and theoptical pickup unit 304 to each other.

The pickup base 317 to write or read information signals to or from anoptical disk placed on the disk table 313 has installed thereon at leasta light source (not shown) such as a semiconductor laser, objective lens312 to focus a light beams emitted from the light source onto the signalrecording surface of the optical disk 302, a photodetector (not shown)to detect a return light from the recording surface of the optical disk302, and a drive system which moves the objective lens 312 toward andaway from the optical disk 302 (in the focusing direction) and acrossthe optical disk 302 (in the tracking direction). Also, the pickup base317 has an insertion hole 317 b formed in one longitudinal end portion317 a thereof and through which the guide shaft 316 is passed, and anengagement piece 330 formed at the other end 317 c thereof opposite tothe end portion 317 a and which is engaged on the guide shaft 316.

As shown in FIG. 5, the pickup base 317 includes also an engagementmember 332 adjacent to the guide shaft 316 and which engages with a leadscrew 331 included in the pickup moving mechanism 318 to move the pickupbase 317. The engagement member 332 is projected to under the lead screw331 from the end portion 317 a through which the insertion hole 317 b isformed, and has a transmission member 333 which engages with the leadscrew 331. The transmission member 333 has provided at an end thereof anengagement projection 334 engaged in threads on the lead screw 331. Thetransmission member 333 is formed from an elastic material such as aleaf spring, so that the engagement projection 334 is kept always inmesh with the threads on the lead screw 331. Having fixed thereto thetransmission member 333 which converts the rotation of the lead screw331 into a linear movement, the pickup base 317 is moved radially of theoptical disk 302 as the lead screw 331 is rotated.

Supported on the pair of guide shafts 316 disposed long the mutuallyopposed lateral edges of the opening 328 in the base chassis 315, thepickup base 317 is guided by the guide shafts 316 in moving between theinner and outer circumferences of the optical disk and the objectivelens 312 is kept exposed to the signal recording surface of the opticaldisk 302 through the opening 328.

As shown in FIG. 6, the pickup moving mechanism 318 includes the leadscrew 331 provided adjacent to the pair of guide shafts 316 an extendingradially of the optical disk, and a DC motor 335 connected to a base end331 a of the lead screw 331 to rotate the lead screw 331.

The lead screw 331 is borne at the end 331 b thereof in a frame 337 bymeans of the base end 331 a and bearing 336. With the frame 337 fixedwith a binding screw or the like to the base chassis 315 of the opticalpickup unit 304, the pickup moving mechanism 318 is provided adjacent toone of the guide shafts 316. The lead screw 331 is threaded, and theengagement member 332 of the pickup base 317 is slidably engaged in withthe threads on the lead screw 331. Therefore, when the lead screw 331 isrotated by the DC motor 335, it can move the pickup base 317 radially ofthe optical disk 302.

As mentioned above, the lead screw 331 is rotated by the DC motor 335and the DC motor 335 will not provide any torque unless it runs at ahigh speed. Therefore, various points of contact of the pickup movingmechanism 318 will be abraded heavily. In case the DC motor 335 isconnected to the lead screw 331 via a gear mechanism to move the pickupbase 317, the operating noise will be increased.

On this account, a step motor is used as the DC motor 335 in the presentinvention and the pickup base 317 is moved radially of the optical disk302 by supplying the DC motor 335 with a rectangular wave for stepwiserun.

The disk tray 303 having the above optical pickup unit 304 housedtherein has formed at a main side 340 a of a generally rectangular traybody 340 thereof a concavity 341 in which the optical disk 302 is to bereceived, and at the rear side of the tray body 340 a compartment 325 inwhich the optical pickup unit 304 is housed. The optical pickup unit 304housed in the compartment 325 has the cover member 343 fixed thereto.The concavity 341 has formed in the bottom thereof an opening 344through which the cover member 343 is exposed. Thus, the cover member343 forms a part of the concavity 341. Also, the disk table 313supporting the objective lens 312 included in the optical pickup unit304 and the optical disk 302 to be rotatable is exposed through theopening 344 in the cover member 343.

The concavity 341 of the disk tray 303 is generally circular, and it isdefined by first to fourth walls 345 to 348 formed generally circular asshown in FIG. 3.

Of the above walls, the first wall 345 is formed at the side of the rearend 303 a of the disk tray 303 to extend over the opening 344 formed inthe bottom of the concavity 341. The first wall 345 has a constantclearance C between the lower edge 345 a thereof opposite to theconcavity 341 and the cover member 343 exposed through the opening 344in the concavity 341.

Note that the second to fourth walls 346 to 348 are generally circularand rise from the concavity 341.

The disk tray 303 is formed by injection molding of a synthetic resinhaving a high rigidity such as PPE (polyphenylene ether), for example.

As shown in FIG. 7, a holding mechanism 360 for holding the disk tray303 inside the device body 301 is formed in the compartment 325 formedthe rear side of the disk tray 303 for housing the optical pickup unit304. The holding mechanism 360 includes a forcing mechanism 361 to forcethe disk tray 303 to outside the device body 301, and an engagementmechanism 362 which is engaged on an engagement projection 326 providedupright on the lower half 307 of the device body 301 to achieve anengagement between the disk tray 303 and device body 301.

The forcing mechanism 361 includes an ejection member 365 to force thedisk tray 303 to outside the device body 301 when pressed to a rear wall301 a of the device body 301, and a coil spring 366 which forces theejection member 365 toward the rear wall 301 a.

The ejection member 365 is shaped to have a generally stick-like shapeand has a flange 365 a formed nearly at the longitudinal middle thereof.Also, the ejection member 365 is disposed in a compartment 368 definedin the disk tray 303. The compartment 368 is formed near one side of thedisk tray 303 to extend in the direction of inserting or ejecting thedisk tray 303. The compartment 368 has a through-hole 368 a formedtherein at the rear end 303 a of the disk tray 303 and a retention step368 b formed nearly in the middle thereof to retain the flange 365 a ofthe ejection member 365. Also, the compartment 368 has a retention wall369 formed in a position inner than the retention wall 368 b andcorrespondingly near the front end 303 b of the disk tray 303 to retainone end of the coil spring 366. The retention wall 369 has formedtherein an insertion hole for the ejection member 365 and also aninsertion space 370 for reception of the ejection member 365. Theinsertion hole 370 is formed in a portion inner than the retention wall369 and further near the front end 303 b of the disk tray 303.

The coil spring 366 is disposed between the retention step 368 a andretention wall 369 of the compartment 368. It has the ejection member365 inserted in the hollow space thereof, and is retained at one endthereof on the flange 365 a of the ejection member 365 and at the otherend on the retention wall 369.

In the forcing mechanism 361 constructed as above, the coil spring 366forces the flange 365 a of the ejection member 365 to the rear end 303 aof the disk tray 303, and thus the ejection member 365 is projected fromthe rear end 303 a as shown in FIG. 7. In this condition, the flange 365a of the ejection member 365 is retained on the retention step 368 b ofthe compartment 368.

Next, when the disk tray 303 is housed in the device body 301, theejection member 365 projecting from the disk tray 303 is butted to therear wall 301 a of the device body 301 and pressed back to the front end303 b of the disk tray 303 against the force of the coil spring 366.Thus, the coil spring 366 is pressed to the flange 365 a of the ejectionmember 365 and compressed to the front end 303 b. When the disk tray 303is engaged on the device body 301 by an engagement mechanism 362 whichwill be described in detail later, the coil spring 366 will keep a forcewhich forces the ejection member 365 toward the rear end 303 a as shownin FIG. 8. It should be noted that at this time, the ejection member 365is passed through the insertion hole formed in the retention wall 369into the insertion space 370.

Then, the disk tray 303 and device body 301 are disengaged by theengagement mechanism 362 from each other, the coil spring 366 forces theflange 365 a of the ejection member 365 to the rear end 303 a. Theejection member 365 will be projected from the rear end 303 a of thedisk tray 303 through the through-hole 368 a, and butted to the rearwall 301 a of the device body 301. As the ejection member 365 is furtherforced, the coil spring 366 extends to the front end 303 b of the disktray 303 from the flange 365 a of the ejection member 365 butted to therear wall 301 a of the device body 301. Therefore, as the retention wall369 is forced to the front end 303 b, the coil spring 366 will eject thedisk tray 303 to outside the device body 301.

Next, there will be explained the engagement mechanism 362 which engageswith the disk tray 5 and device body 7 when the disk tray 5 is insertedinto the device body 7.

As shown in FIG. 9, the engagement mechanism 362 includes an engagementprojection 326 provided on the lower half 307 of the device body 301 forengagement with the disk tray 303 to retain the disk tray 303 engaged inthe device body 301, and an engagement piece 371 provided on the disktray 303 and pivoted in a direction for engagement on the engagementprojection 326.

The engagement projection 326 is provided near one end of the lower half307 of the device body 301 as will be seen in FIG. 1. The engagementprojection 326 is formed to be generally cylindrical. When the disk tray303 is inserted into the device body 301, the engagement projection 326will be engaged on the engagement piece 371 formed at the disk tray 303to hold the latter inside the device body 301.

As shown in FIG. 9, the engagement piece 371 engaged on the engagementprojection 326 includes a retaining portion 372 formed like a hook tocatch the engagement projection 326, a body 373 having the retainingportion 372 formed at the end thereof, a stud 374 provided at the sideof the base end of the body 373 and about which the engagement piece 371is pivoted, and an abutting portion 376 to be put into contact with aneject button 375 which will be described in detail later. The engagementpiece 371 is pivotable about the stud 374 in the direction of arrow D inFIG. 9 or in a direction opposite to the direction of arrow D. A torsioncoil spring 377 is wound on the stud 374 to always force the engagementpiece 371 for pivoting in the direction of arrow D in FIG. 9. With theengagement piece 371 pivoted in the direction of arrow D in FIG. 9, theretaining portion 372 is positioned on the moving orbit of theengagement projection 326 provided on the device body 301.

Note that the eject button 375 put in contact with the abutting portion376 is provided on a control panel (not shown) formed at the front end301 b of the device body 301. When the user presses the eject button 375for drawing out the disk tray 303, it presses the abutting portion 376to pivot the engagement piece 371 in the direction opposite to thedirection of arrow D in FIG. 9.

The engagement piece 371 has a bevel 373 a formed thereon to extend fromthe end of the body 373 in the moving direction of the engagementprojection 326 and protrude in the direction of arrow D. The hook-shapedretaining portion 372 is formed at the protruding end of the bevel 373a. Also, the engagement piece 371 has the abutting portion 376 formed atthe side thereof opposite to the side where the bevel 373 a is formed.Namely, the stud 374 is located between the abutting portion 376 andbevel 373 a. Therefore, when the abutting portion 376 is pressed by theeject button 375, the engagement piece 371 is pivoted in the directionopposite to the direction of arrow D in FIG. 9. As the retaining portion372 is thus pivoted in the direction of arrow D, it catches theengagement projection 326 and holds the disk tray 303 inside the devicebody 301. When the retaining portion 372 is pivoted in the directionopposite to the direction of arrow D to release the engagementprojection 326, thus allowing the disk tray 303 to be ejected frominside the device body 301 by the aforementioned coil spring 366 andejection member 365.

More specifically, as the disk tray 303 is inserted into the device body301, the engagement projection 326 provided on the lower half of thedevice body 301 moves in the direction of arrow H in FIG. 9, abuts thebevel 373 a, and thus pivots the engagement piece 371 in a directionopposite to the direction of arrow D. When the engagement projection 326has moved over the end of the bevel 373 a, the engagement piece 371 ispivoted in the direction of arrow D under the force of the torsion coilspring 377 and the retaining portion 372 is positioned again on themoving orbit of the engagement projection 326. Thus, the engagementpiece 371 has the retaining portion 372 thereof engaged on theengagement projection 326 and the disk tray 303 engages with the devicebody 301.

For ejection of the disk tray 303 to outside the device body 301, theuser operates the eject button 375 which will press the abutting portion376. When the abutting portion 376 is pressed by the eject button 375,the engagement piece 371 is pivoted in the direction opposite to thedirection of arrow D in FIG. 9. When the engagement piece 371 is thuspivoted in the direction of arrow D, the retaining portion 372 isretracted from the moving orbit of the engagement projection 326 andthus released from the engagement projection 326. Thus, the disk tray303 and device body 301 are disengaged from each other, and the disktray 303 is forced out of the device body 301 by the aforementionedforcing mechanism 361.

The disk tray 303 constructed as above has also an engagement portion349 formed on each of the opposite lateral sides of the tray body 340and which engages with the guide member 308 formed on the lower half307. Since the engagement portion 349 is slidably engaged on the guidemember 308, the disk tray 303 is guided in moving into, or to outside,the device body 301, and thus carried along with the optical pickup unit304 into, or to outside, the device body 301.

As shown in FIG. 10, the FPC (flexible printed circuit) 310 connectingthe optical pickup unit 304 housed in the disk tray 303 and the printedwiring board 309 provided on the lower half 307 of the device body 301to each other is shaped to have a generally U-shaped form, and includesfirst and second linear arm portion portions 350 and 351 adjacent toeach other and extending in parallel, and a circular portion 352 joiningthe first and second arm portion portions 350 and 351 to each other.

The first arm portion 350 is directed at the end thereof toward the rearend 307 d of the lower half 307 and connected to a connector (not shown)provided at the bottom of the printed wiring board 309. Also, the firstarm portion 350 is fixed to the bottom of the lower half 307. The secondarm portion 351 contiguously joined to the first arm portion 350 via thecircular portion 352 has the end portion 351 a folded back toward thefront end 307 a of the lower half 307 and connected to the connector 354provided on the optical pickup unit 304 housed in the disk tray 303. Thesecond arm portion 351 is not fixed to the device body 301 and disk tray303, but as the disk tray 303 is moved, the second arm portion 351 ismoved into, or to outside, the device body 301 with the circular portion352 being taken as a reference position.

More particularly, as the disk tray 303 is moved into, or to outside,the device body 301, the FPC 310 has also the second arm portion 351thereof moved into the device body 301 as shown in FIGS. 11A to 11C. Atthis time, the second arm portion 351 is folded back toward the frontend 307 a of the lower half 307, resulting in a bending 355. As the disktray 303 is moved, the bending 355 shifts in the moving direction of thedisk tray 303. Namely, when the disk tray 303 is ejected to outside thedevice body 301, the second arm portion 351 of the FPC 310 is alsofolded back in a position near the circular portion 352 and has the endportion 351 a thereof ejected to outside the device body 301 as shown inFIG. 11A. Thus, the bending 355 is formed in a position near thecircular portion 352. Then, as the disk tray 303 is moved into thedevice body 301, the bending 355 of the second arm portion 351 of theFPC 310 shifts toward the end portion 351 a correspondingly as shown inFIG. 11B. When the disk tray 303 is fully housed in the device body 301,the bending 355 of the second arm portion 351 of the FPC 310 is formedin a position near the connection with the connector 354 provided on theoptical pickup unit 304 as shown in FIG. 11C.

For accurate writing or reading data to or from an optical disk used inthe CD-R/RW or DVD-ROM, a light beam emitted from the optical pickupshould be incident perpendicularly upon the signal recording surface ofthe optical disk. For such an optical disk drive, the relevant Standardpermits a fixed range of the angle formed between the signal recordingsurface of the optical disk and the optical axis of the objective lenswhich focuses the light beam onto the optical disk.

Also, in such an optical disk drive, in case a light beam is notincident perpendicularly upon the signal recording surface of theoptical disk, the angle of the light beam in relation to the signalrecording surface is detected, and the relation in angle between theobjective lens which focuses the light beam and the signal recordingsurface of the optical disk is adjusted by a skew adjusting mechanism.

As shown in FIG. 4, the skew adjusting mechanism 400 is provided insidethe base chassis 315 in which the pickup base 317 is provided. It isprovided at each of the opposite ends of each of the guide rails 316 inpair which guide the pickup base 317 in moving radially of the opticaldisk 302. As shown in FIG. 12, the skew mechanism 400 includes a spring402 disposed in a holder 401 fitted on one end of the guide rail 316 andwhich supports the upper portion of the guide rail 316, and an adjustingscrew 403 provided to abut the lower side of the guide rail 316 andwhich presses the guide rail 316 vertically to adjust the height of theguide rail 316.

The above holder 401 is installed to a rear side 405 a of a main plate405 included in the base chassis 315, and has formed therein aninsertion opening 406 in which the end portion of the guide rail 316 isinserted. The holder 401 has the end portion of the guide rail 316inserted therein through the insertion opening 406, and the spring 402provided therein as shown in FIG. 12. The holder 401 has also formed inthe bottom of the insertion opening 406 a screw hole 407 in which thereis inserted an adjusting screw 403.

The spring 402 is a cylindrical coil spring and forces the guide rail316 downward. The adjusting screw 403 is inserted in the screw hole 407formed in the bottom of the holder 401 and abuts, at the top thereof,the lower side of the guide rail 316.

The above skew adjusting mechanism 400 adjusts the height of the guiderail 316 by adjusting the length, projected into the holder 401, of theadjusting screw 403. Thus, the relation in angle between the objectivelens 312 which focuses the light beam and the signal recording surfaceof the optical disk 302 can be adjusted so that the light beam can beincident perpendicularly upon the signal recording surface.

However, the thickness of the skew adjusting mechanism 400 is a problemin implementing a demanded thinner and more compact design of theoptical disk drive. That is, in case the thickness of the VDV-ROM drivecasing, for example, is adapted to that of a hard disk drive having athickness of 9.5 mm in order to reduce the thickness of the disk driveitself, no other than the adjusting margin for the height of the guiderail 316 can be reduced since the parts of the disk drive are fixed inheight. Therefore, it is almost difficult to reduce the thickness of thedisk drive.

Note here that the DC motor 335 included in the pickup moving mechanism318 includes a generally rectangular housing 338 which covers the basechassis 315 as a whole including the width, as shown in FIG. 6A.Therefore, the housing 338 has a width (6 mm, for example) equivalent tothe thickness of the base chassis 315 as shown in FIG. 6B.

Also, the thickness of the pickup moving mechanism 318 is a problem inimplementing the above demanded thinner and more compact design of theoptical disk drive. Namely, in case the thickness of the VDV-ROM drivecasing, for example, is adapted to that of the hard disk drive having athickness of 9.5 mm in order to reduce the thickness of the disk driveitself, covering the entire housing 338 of the DC motor 335 with ametallic plate will make it difficult to reduce the thickness of thedisk drive to 9.5 mm since the parts of the disk drive are fixed inheight.

Note that in the aforementioned optical pickup unit 304, thetransmission member 333 is formed from an elastic material such as aleaf spring or the like and the engagement projection 334 is forced bythe leaf spring to always be in mesh with the threads on the lead screw331. Therefore, to move the pickup base 317 stepwise to a desiredposition by the DC motor 335 supplied with a predeterminedrectangular-wave pulse, the engagement projection 334 has to be movablewithout being disengaged from the threads on the lead screw 331. On thisaccount, the transmission member 333 should has the engagementprojection 334 thereof engaged in the threads on the lead screw 331under a strong force.

Since the DC motor 335 as a step motor provides only a weak torque,however, if the transmission member 333 is engaged in the threads on thelead screw 331 under an excessively strong force, the lead screw 331cannot be rotated and thus the pickup base 317 cannot be moved quickly.

On the other hand, if the force for application to the transmissionmember 333 is weakened, the engagement projection 334 will be disengagedfrom the threads on the lead screw 331, supply of the rectangular-wavepulses for a predetermined number of steps to the DC motor 335 cannotmove the pickup base 317 to a predetermined position and thuspositioning of the pickup base 317 is inconveniently impossible.

Note here that in the disk drive 300, since the disk tray 303 formedfrom PPE, optical pickup unit 304 formed from iron and cover member 343formed from aluminum are joined to each other, their differences incoefficient of linear thermal expansion from one another will cause eachof the components to be distorted as the component has a highertemperature. That is, as mentioned above, the disk tray 303 is formedfrom a rigid material such as PPE (polyphenylene ether), the basechassis 315 of the optical pickup unit 304 housed in the disk tray 303is formed from iron (Fe), and the cover member 343 installed to the topof the base chassis 315 and exposed through the opening 344 in the disktray 303 is formed from aluminum (Al). Namely, these disk tray 303, basechassis 315 and cover member 343 are different in linear expansioncoefficient from each other. More specifically, the linear expansioncoefficient of PPE is 2.8×10⁻⁵/mm° C., while the linear expansioncoefficient of aluminum is 2.4×10⁻⁵/mm° C. and that of iron is1.2×10⁻⁵/mm° C.

Each of the disk tray 303, base chassis 315 and cover member 343 isdistorted due to such differences in linear expansion coefficient,namely, due to differences in thermal shrinkage, as they are elevated intemperature when the disk drive 300 is driven. More particularly, thealuminum-made cover member 343 is warped from the lateral edge of theopening 344 toward the optical disk 302 and will have a sliding contactwith the signal recording surface of the optical disk 302 received inthe concavity 341 in some cases. Particularly, since there is defined aclearance C between the lower edge of the first wall 345 and the covermember 343 (see FIG. 3), the cover member 343 will be bent toward theclearance C. Also, since the first wall 345 is located along the outercircumference of the optical disk 302 and thus incurs a relatively largeaxial runout, it is likely to have a sliding contact with the covermember 343.

Note here that in the aforementioned disk drive 300, the holdingmechanism 360 for holding the disk tray 303 inside the device body 301is provided to disengage the engagement mechanism 362 from theengagement projection 365 by means of the eject button 375. If the ejectbutton 375 is pushed by mistake while data is being written to or readfrom the optical disk 302, the disk tray 303 and device body 301 aredisengaged from each other, possibly causing a trouble in the data writeor read.

Also note here that in order to prevent the FPC 310 from being caughtbetween the device body 301 and the rear side 302 a of the disk tray 303while the disk tray 303 is being housed into the device body 301, theFPC 310 is formed to have the first arm portion 351 changed in rigidityin places.

That is to say, when the disk tray 303 is outside the device body 301, aclearance 356 is defined between the disk tray 303 and device body 301as shown in FIG. 11A. Therefore, if the end portion 351 a of theflexible FPC 310 is bent to below the clearance 356 when the disk tray303 is housed into the device body 301, the FPC 310 will be caughtbetween the disk tray 303 and device body 301 as shown in FIG. 13.

On this account, the FPC 310 has a cover lay 357 attached on the endportion 351 a of the second arm portion 351. The cover lay 357 increasesthe rigidity of the end portion 351 a of the second arm portion 351 incomparison with that of the rear end portion 351 b. Therefore, the FPC310 is prevented from being bent at the higher-rigidity end portion 351a thereof to below the clearance 356 when the disk tray 303 once ejectedto outside the device body 301 is housed again into the device body 301,while the lower-rigidity, flexible rear end portion 351 b of the secondarm portion 351 is bent, so that the disk tray 303 is positively movedinto the device body 301.

However, when the disk tray 303 is fully housed in the device body 301,the FPC 310 having the cover lay 357 attached on the end portion of thesecond arm portion 351 will have the bending 355 of the second armportion 351 thereof shifted toward the end portion 351 a and thus thebending 355 be formed in a position near the connection with theconnector 354 provided on the optical pickup unit 304 as shown in FIG.11C. The nearer to the connection with the connector 354, the larger theload to the bending 355 becomes. For a longer distance between theconnection with the connector 354 and the bending 355, however, the FPC310 should have an extra length, which will add to the cost ofmanufacture. Also, the cover lay 357 attached on the end portion 351 aof the second arm portion 351 increases the rigidity and thus the loadto the end portion 351 a as well. Further, since the thickness of thedevice body 301 of the disk drive 300 is minimized to meet therequirement for the thinner design of a host device in which the diskdrive 300 is to be used, the curvature of the bending 355 will be largeras the device body 301 is designed thinner and thus the load to thebending 355 be larger.

As the disk tray 303 is repeatedly inserted and ejected with a largeload being applied to the second arm portion 351 of the FPC 310 at eachtime, the end portion 351 a of the second arm portion 351 will crack andthe circuit pattern formed in the FPC 310 will be broken.

OBJECT AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to overcome theabove-mentioned drawbacks of the related art by providing an improvedrecording and/or playback apparatus.

The above object can be achieved by providing a recording and/orplayback apparatus including, according to the present invention, abase; a disk rotation driving mechanism which supports an optical diskand rotates the optical disk; an optical pickup which focuses a lightbeam emitted from a light source by an objective lens onto a recordingsurface of the optical disk and detects a return light from the opticaldisk; a guide means having a first guide shaft which supports the oneend of the optical pickup and a second guide shaft which supports theother end of the optical pickup, the first and second guide shafts beingdisposed on the base in parallel to each other radially of the opticaldisk; an optical pickup driving means guided by the first and secondguide shafts to move the optical pickup radially of the optical disk;and a skew adjusting means including an elastic member which provides aforce to the first and second guide shafts in a direction generallyperpendicular to the main side of the optical disk and an adjustingscrew which is in contact with the first and second guide shafts fromthe opposite side of the elastic member, and which adjust a skew byadjusting the inclination of the first and second guide shafts by theadjusting screw.

Also the above object can be achieved by providing a recording and/orplayback apparatus including, according to the present invention, abase; a disk rotation driving mechanism which supports an optical diskand rotates the optical disk; an optical pickup which focuses a lightbeam emitted from a light source by an objective lens onto a recordingsurface of the optical disk and detects a return light from the opticaldisk; a guide means having a first guide shaft which supports the oneend of the optical pickup and a second guide shaft which supports theother end of the optical pickup, the first and second guide shafts beingdisposed on the base in parallel to each other radially of the opticaldisk; an optical pickup driving means guided by the first and secondguide shafts to move the optical pickup radially of the optical disk;and a skew adjusting means including an elastic member which provides aforce to the first and second guide shafts in a direction generallyperpendicular to the main side of the optical disk and an adjustingscrew which is in contact with the first and second guide shafts fromthe opposite side of the elastic member, and which adjust a skew byadjusting the inclination of the first and second guide shafts by theadjusting screw, the adjusting screw being electroconductive or beingplated to be electroconductive and having a ground potential.

Also the above object can be achieved by providing a recording and/orplayback apparatus including a pickup moving mechanism using a stepmotor which includes, a lead screw engaged in a pickup chassis andhaving engaged thereon a feeding member which feeds the pickup chassisradially of a disk-shaped recording medium; a magnet rotated along withthe lead screw; a magnetic coil which acts on the magnet to rotates thelead screw; and a housing which houses the magnet and magnetic coil, thehousing having an opening formed in each of the upper and lower sidesthereof and between a concavity in a disk tray having the pickup chassisinstalled therein and a bottom plate which supports the bottom of thedisk tray.

Also the above object can be achieved by providing a recordingand/playback apparatus including an optical pickup unit having anobjective lens disposed therein; a pickup moving mechanism to move theoptical pickup unit; and an engagement member which engages an pickupbase of the optical pickup unit and the pickup moving mechanism witheach other, the engagement member including an engagement projectionengaged in threads formed on a lead screw; and a compartment providedcontiguously to the pickup base to house a clearance definition memberwhich retains the engagement projection at a distance which assures theengagement on the lead screw, the clearance definition member beinghoused in isolation from the wall of the compartment by a clearancesmaller than the depth of engagement of the engagement projection in thethreads on the lead screw.

Also the above object can be achieved by providing a recording and/orplayback apparatus including, according to the present invention, anoptical pickup unit including a pickup base; a pickup moving mechanismincluding a lead screw which moves the pickup base; and an engagementmember including a side wall fixed to the pickup base and having formedoutside thereof an engagement projection engaged on the lead screw; acompartment having housed therein a clearance definition member whichsupports the inner surface of the side wall to maintain a distance thatassures the engagement between the engagement projection and lead screw;and a hinge provided on the base end of the side wall and flexible in adirection in which the side wall is moved toward or away from the leadscrew, the clearance definition member including a support pieceextending along the inner surface of the side wall toward outside thecompartment.

Also the above object can be achieved by providing a recording and/orplayback apparatus including, according to the present invention, apickup chassis having provided thereon an optical pickup, pickup movingmechanism and a disk rotation driving mechanism; a cover member havingformed therein an opening through which the pickup and disk table facethe recording surface of a disk-shaped recording medium and which isconnected to the pickup chassis to form a part of a concavity in whichthe disk-shaped recording medium is to be received; and a disk trayhaving formed therein the disk-shaped recording medium receivingconcavity, generally circular, and having formed therein an openingthrough which the cover member faces directly the recording surface ofthe disk-shaped recording medium and which is closed by the cover memberwhen the latter is connected to the pickup chassis, the pickup chassis,cover member and disk tray being formed from materials different incoefficient of thermal expansion from each other; the disk tray having aprojection provided on a wall provided at the outer-circumferential sideof the concavity and extending to above the opening to maintain aclearance between the outer-circumferential wall and the cover memberwhich closes the opening.

Also the above object can be achieved by providing a recording and/orplayback apparatus including, according to the present invention, adevice body; a disk tray which is moved into, or to outside, the devicebody; a disk rotation driving mechanism provided on the disk tray torotate a disk-shaped recording medium; an optical pickup to write and/orread information signals to and/or from the disk-shaped recordingmedium; a pickup moving mechanism to move the optical pickup between theinner and outer circumferences of the disk-shaped recording medium; anda disk tray holding mechanism to hold the disk tray inside the devicebody, the disk tray holding mechanism including a forcing member toforce the disk tray to outside the device body; an engagement projectionprovided at the device body and which engages with the disk tray to keepthe disk tray engaged inside the device body; an engagement pieceprovided on the disk tray and which is pivoted in a direction in whichthe engagement projection is inserted inside the device body; a pivotingpiece which gets into touch with the engagement piece to limit thepivoting range of the engagement piece, to thereby engage the engagementpiece onto the engagement projection or disengage the engagement piecefrom the engagement projection; a plunger which is engaged with thepivoting piece and inserted into a magnetic coil to pivot the pivotingpiece; and a pressing piece which is put into contact with the pivotingpiece when pressed by the engagement projection and thus presses thepivoting piece in a direction in which the engagement piece is engagedonto the engagement projection, when the disk tray is inserted into thedevice body against the force of the forcing member, the engagementpiece pressing the pressing piece, the pivoting piece thus put intocontact with the pressing piece being pivoted in a direction in whichthe engagement piece is engaged onto the engagement projection and theengagement piece being thus engaged on the engagement projection,whereby the disk tray is held inside the device body; and when theplunger pivots the pivoting piece, the engagement piece being forced ina direction in which it is disengaged from the engagement projection,whereby the disk tray is ejected to outside the device body under theforce of the forcing member.

Also the above object can be achieved by providing a recording and/orplayback apparatus including, according to the present invention, achassis; a moving member including a recording medium mount on which arecording medium is to be placed and which is supported by the chassisto be movable and thus movable between a recording medium changeposition where it is projected forward from the chassis and a recordingmedium home position inside the chassis; and a flexible cable havingfirst and second arm portions and which is flat and generally U-shaped,the first arm portion being fixed by connection to a connector with theend thereof directed to the back of the chassis, at least a part of thesecond arm portion of the flexible cable being flexibly bent when themoving member is moved; and the part of the flexible cable, flexiblybent when the moving member is moved between the recording medium changeposition and recording medium home position, being smaller in thicknessthan the other part of the flexible cable.

In the above recording and/or playback apparatus including the skewadjusting mechanism according to the present invention, the height ofthe guide shafts is adjusted by pinching the end portion of the guideshaft included in the guide means supporting the optical pickup unitbetween the conical elastic member and adjusting screw. Thus, the freeend of the elastic member, abutting the guide shaft, is compressed whilegoing into the bore of the base end portion having a larger diameter.Therefore, the elastic member according to the present invention can besmaller in compressed length as compared with a cylindrical elasticmember, so that the height of the entire skew adjusting mechanism can besmaller. Thus, the chassis can be designed thinner.

In the recording and/or playback apparatus including the skew adjustingmechanism according to the present invention, the adjusting screw whichpinches the guide shaft is electroconductive or plated to beelectrically conductive to have a ground potential. Thus, the skewadjusting mechanism can be connected to the ground potential by theguide shafts. Thus, it is possible to suppress the noise taking placedue to the electrical charging of the guide shafts.

Also, the step motor according to the present invention is designed thinsince the housing is open at both the top and bottom thereof. Thehousing is held tight between the cover member and bottom plate disposedat the top and bottom, respectively, of the optical pickup unit.

As above, the magnetic field of the magnetic coil placed in the motorhousing can be closed, so that the fringe magnetic field from the stepmotor can be inhibited from adversely affecting write or read ofinformation signals to or from the optical disk. Also, since the stepmotor housing is open at both the top and bottom thereof, the heat caneasily be discharged from inside the housing.

Further, in the recording and/or playback apparatus according to thepresent invention, the engagement projection, formed in the compartment,of the engagement member connected to the pickup base provided with theobjective lens engages with the threads on the lead screw for the depthof the threads, and the elastic member is housed inside the compartmentin isolation from the engagement member by a clearance smaller than thedepth of engagement of the engagement projection in the threads on thelead screw between the side walls of the compartment.

Therefore, the elastic member is housed with the engagement projectionthereof formed on the compartment wall not being forced by the leadscrew, whereby it is possible to prevent the lead screw from beingapplied with an excessive force which will dull the rotation of the leadscrew and thus block the movement of the pickup base.

Also, even a misalignment between the engagement projection and threadson the lead screw, if any caused due to the dimensional tolerance of theengagement member or the like during movement of the pickup base, can belimited to within the clearance defined between the wall of thecompartment and side wall of the elastic member. Thus, the engagementprojection of the engagement member will not have any misalignmentlarger than the depth of engagement thereof in the threads on the leadscrew and it is possible to prevent the lead screw and engagementprojection from being disengaged from each other in the course of thepickup base being moved.

In the recording and/or playback apparatus according to the presentinvention, when the clearance definition member is received in thecompartment of the engagement member, the support piece can support theside wall of the compartment over the rightward and left widths.Therefore, while the pickup base is being moved or when the recordingand/or playback apparatus incorporating the engagement member fallsdown, the clearance definition member will relieve the load concentratedto the hinge formed on the engagement member installed integrally withthe pickup base which supports the side wall having formed thereon theengagement projection which is engaged on the lead screw. Thus, theclearance definition member can prevent the recording and/or playbackapparatus from being damaged.

In the above recording and/playback apparatus according to the presentinvention, the disk tray, base chassis and cover member are formed frommaterials different in coefficient of linear thermal expansion from eachother. Even if each of these components is thermally deformed while datais being written to or read from the optical disk, the cover memberabuts the projection formed on the lower edge of the body of thecompartment wall of the disk tray and is thus prevented from warpingtoward the optical disk. Thus, the cover member can be prevented fromhaving a sliding contact with the optical disk.

Also, in the recording and/or playback apparatus including theengagement mechanism according to the present invention, when the disktray is ejected from inside the device body, the coil on a core issupplied with a current to cancel the magnetic force of the incorporatedmagnet. The pivoting piece opens the pivoting area so that theengagement portion thereof will retract from on the moving orbit of theengagement projection. Thus, the engagement projection is disengagedfrom the engagement portion of the pivoting piece and the disk tray isdisengaged from the device body.

Therefore, since the magnetic force of the magnet magneticallyattracting the plunger is canceled by supplying the current to theon-core coil, it is possible to prevent the disk tray from being drawnout due to an erroneous operation by the user while data is beingwritten to or read from the optical disk. Thus, the disk tray canpositively be inserted into place and ejected from there.

Also in the above recording and/or playback apparatus according to thepresent invention, when the moving member is housed in the chassis, thesecond arm portion of the flexible cable is bent at a portion thereofnear the connection with the connector. Since the portion of the secondarm portion near the connection is smaller in rigidity than the otherportion, however, the bending-caused load to the second arm portion canbe reduced. Therefore, the second arm portion can be prevented frombeing cracked at the free end thereof, so that the circuit pattern willnot be broken.

Also, the flexibly bendable portion of the second arm portion isintended to reduce the bending-caused load when the second arm portionis bent in the portion thereof near the connection with the connector.The distance between the connection and bent portion may not be long toreduce the load applied to the second arm portion when the moving memberis housed into the chassis to the second arm portion. Thus, the secondarm portion may not excessively be long, which advantageously leads to areduction of the cost of manufacture.

Further, in the recording and/or playback apparatus of the thinnerdesign, since the height of the flexible cable when the moving member ishoused in the chassis is minimized, the curvature of the bent portion ofthe cable is larger and a larger load will be applied to the bentportion. However, the load to the bent portion of the second arm portionwhen the moving member is housed into the chassis can be reduced, whichalso advantageously leads to the thin design of the chassis.

These objects and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription of the preferred embodiments of the present invention whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of the conventional disk drive;

FIG. 2 is a perspective view of the disk drive in FIG. 1;

FIG. 3 is a perspective view of a disk tray used in the disk drive inFIG. 1;

FIG. 4 is a perspective view of an optical pickup unit provided with aconventional skew adjusting mechanism;

FIG. 5 is a perspective view of a pickup moving mechanism used in thedisk drive in FIG. 1;

FIG. 6 is also a perspective view of the pickup moving mechanism in FIG.5;

FIG. 7 is a rear view of the disk tray in FIG. 3;

FIG. 8 is also a rear view of the disk tray in FIG. 7;

FIG. 9 is a plan view of an engagement mechanism used in the disk drivein FIG. 1;

FIG. 10 is a plan view of a flexible printed wiring board used in thedisk drive in FIG. 1;

FIG. 11 is a sectional view of the disk drive in FIG. 1;

FIG. 12 is a sectional view of the skew adjusting mechanism in FIG. 4;

FIG. 13 is a sectional view of the disk tray and device body with theflexible printed wiring board being placed between them;

FIG. 14 is a perspective view of a notebook computer having installedtherein the recording and/or playback device according to the presentinvention;

FIG. 15 is an exploded perspective view of the recording and/or playbackdevice according to the present invention;

FIG. 16 is a sectional view of the recording and/or playback device inFIG. 15;

FIG. 17 is a rear vide of the disk tray in FIG. 16;

FIG. 18 is also a rear view of the disk tray in FIG. 16;

FIG. 19 is a plan view of an engagement mechanism used in the recordingand/or playback device in FIG. 15;

FIG. 20 is also a plan view of the engagement mechanism in FIG. 19;

FIG. 21 is a plan view of an optical pickup unit used in the recordingand/or playback device in FIG. 15;

FIG. 22 is a sectional view of a skew adjusting mechanism used in therecording and/or playback device in FIG. 15;

FIG. 23 is a sectional view of a variant of the skew adjusting mechanismin FIG. 22;

FIG. 24 is a sectional view of another variant of the skew adjustingmechanism in FIG. 22;

FIG. 25 is a plan view of a pickup moving mechanism used in therecording and/or playback device in FIG. 15;

FIG. 26 is a perspective view of an engagement member used in therecording and/or playback device in FIG. 15;

FIG. 27 is an exploded perspective view of the engagement member in FIG.26;

FIG. 28 is a side elevation of the engagement member in FIG. 26;

FIG. 29 is a plan view of the optical pickup unit having a cover memberattached thereto;

FIG. 30 is a perspective view of a variant of the engagement member inFIG. 26;

FIG. 31 is a perspective view of the engagement member (shown in FIG.30) having a gap defining member housed in a compartment;

FIG. 32 is a plan view of the engagement member in FIG. 31;

FIG. 33 is a perspective view of another variant of the engagementmember in FIG. 26;

FIG. 34 is a plan view of the engagement member (shown in FIG. 33)having a gap defining member housed in a compartment;

FIG. 35 is a plan view of the engagement member in FIG. 34;

FIG. 36 is a perspective view of the disk tray having a concavity forreceiving a disk;

FIG. 37 is a plan view a flexible printed wiring board for connectingthe disk tray and device body to each other;

FIG. 38 is a perspective view of the disk tray and device body connectedby the flexible printed wiring board to each other;

FIG. 39 is a section view of the flexible printed wiring board when thedisk tray is moved between two positions inside and outside the device;

FIG. 40 is a block diagram of the recording and/or playback deviceaccording to the present invention;

FIG. 41 explains an area in which the optical pickup unit is movedstepwise;

FIG. 42 shows a sequence of operations made in pulsed driving of theoptical pickup unit at start-up of the recording and/or playback device;and

FIG. 43 shows a sequence of operations made in pulsed driving of theoptical pickup unit at disk ejection in the recording and/or playbackdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The disk recording and/or playback apparatus according to the presentinvention (will be referred to as “disk recorder/player” hereunder) willbe described in detail with reference to the accompanying drawings. Therecorder/player, generally indicated with a reference number 1, is adisk drive for playback of an optical disk such as CD (compact disk),DVD (digital versatile disk) and the like. It is to be installed in thedrive bay of a host apparatus such as a notebook computer or the like asshown in FIG. 14.

Referring now to FIG. 15, the disk recorder/player 1 is schematicallyillustrated in the form of an exploded perspective view. As shown, thedisk recorder/player 1 includes a disk tray 5 having an optical disk 4such as a DVD or the like placed therein, and an optical pickup unit 6connected to the disk tray 5 to read information signals from theoptical disk 4 placed on the disk tray 5. Also, correspondingly to thecompact and thin design of the host apparatus 2 in which the diskrecorder/player 1 is installed, the disk recorder/player 1 has a body(will be referred to as “device body” wherever appropriate hereinafter)7 designed to have a height of about 9.5 mm, which is the same height ofthe hard disk drive, for example, as shown in FIG. 16. In the devicebody 7 having the height or thickness of 9.5 mm, the geometry of eachcomponent is as follows. That is, the optical disk 4 is 1.2 mm high orthick, the axial runout of the optical disk 4 is ±0.5 mm, the disk tray5 connected to the optical pickup unit 6 is 5.2 mm high, clearancedefined between the surface, on which the optical disk 4 is placed, ofthe disk tray 5 and the optical disk 4 is 0.4 mm thick, clearancedefined between the disk tray 5 and the bottom of the device body 7 is0.4 mm, and the upper and lower halves 8 and 9 joined to each other toform an outer casing of the device body 7 are 0.4 mm and 0.5 mm,respectively, thick.

The body 7 of the disk recorder/player 1 is composed of the upper andlower halves 8 and 9 butt-joined to each other. The upper and lowerhalves 8 and 9 are formed by punching and drilling a metallic plate.

The lower half 9 of the device body 7 has disposed thereon a circuitboard 17 on which there are formed a control circuit for controlling theoperation of the disk recorder/player 1, an interconnecting connectorfor connection of the disk recorder/player 1 to the host apparatus 2,etc. Also, the lower half 9 is open at one end thereof at which the disktray 5 is drawn to outside the device body 7, and has a rear wall 9 aformed at an end thereof opposite to the open end. The lower half 9 hasalso rising side walls 9 b and 9 c formed along the opposite edgesthereof between which there are provided the open end and rear wall 9 a.

On the opposite side walls 9 b and 9 c, guide rails 12 to guide the disktray 5 for insertion into, and ejection from, the device body 7 areprovided to extend from the rear wall 9 a to the open end of the lowerhalf 9. Each of the guide rails 12 is shaped to have a generallyC-shaped section and has a C-shaped concavity 12 a formed therein towardthe device body 7. The guide rail 12 has slidably engaged in theconcavity 12 a thereof a guide member 13 connected to the disk tray 5.Also, the guide rail 12 has formed thereon a stopper 14 which limits thesliding range of the guide member 13 in order to prevent the disk tray 5from being drawn out of the device body 7 to more than a predeterminedlength.

The guide member 13 engaged in the guide rail 12 is shaped to have agenerally C-shaped section, and holds the disk tray 5 at the oppositesides to be slidable. When the disk tray 5 is ejected from, or insertedinto, the device body 7, the guide member 13 slides on the guide rail 12to guide the disk tray 5 for smooth movement.

Also, the lower half 9 has provided a rising engagement projection 11which is engaged in a holding mechanism 18 which holds the disk tray 5inside the device body 7. The holding mechanism 18 will be described indetail later. In addition, the lower half 9 has provided thereon nearthe rear wall 9 a a printed wiring board 17 having a drive circuitformed thereon. The printed wiring board 17 includes a so-called rigidcircuit substrate. It has a wiring pattern formed thereon and hasmounted on the wiring pattern also various electronic parts such as aconnector for connection to an external apparatus. Also, the printedwiring board 17 has mounted thereon an FPC (flexible printed circuit) 23connected to the optical pickup unit 6. The FPC 25 will be described indetail later.

The disk tray 5 inserted into, and ejected to outside, the device body 7has formed therein a concavity 15 in which the optical disk 4 is to bereceived. This concavity 15 is generally circular, and has formed in themain side thereof an opening 16 through which a disk table and objectivelens of the optical pickup unit 6 housed in the disk tray 5 facesdirectly the optical disk 4. The opening 16 extends nearly from thecenter of the concavity 15 to the front end 5 a of the disk tray 5.Also, a cover member installed to a base chassis of the optical pickupunit 6 and the disk table and objective lens installed on the basechassis and facing upward through the cover member are exposed to theoptical disk 4 through the opening 16.

The disk tray 5 is formed from a rigid PPE (polyphenylene ether)containing glass in 20%. The generally circular concavity 15 in whichthe optical disk 4 is to be received is formed on a main side 5 b of thedisk tray 5, and the holding mechanism 18 holding a compartment 21 inwhich the optical pickup unit 6 is housed and the disk tray 5 engagedinside the device body 7 is formed on a rear side 5 c of the disk tray 5as shown in FIG. 17. The optical pickup unit 6 will be described indetail later.

The compartment 21 has provided therein a plurality of engagementprojections 25 that engage with the optical pickup unit 6. When theengagement projections 25 are engaged in a plurality of engagement holesformed in the base chassis of the optical pickup unit 6, the compartment21 is connected to the optical pickup unit 6.

The disk tray 5 has formed thereon a guide projection 22 extending in adirection in which the disk tray 5 is inserted into, and ejected tooutside, the device body 7 and which is engaged on the guide member 13.The guide projection 22 is held slidably in the aforementioned guidemember 13 to guide insertion and ejection of the disk tray 5 in relationto the device body 7. Also, the guide projection 22 has stop piecesprovided at each of ends at the rear end 5 d thereof at the device body7 and at the front end 5 a toward the disk tray 5 is to be drawn out.The stop pieces will not be described in detail herein. They areintended to prevent the disk tray 5 from being disengaged from the guidemember 13 and projected to the front end 5 a of the guide member 13.

The disk tray 5 has provided thereon the holding mechanism 18 whichholds the disk tray 5 inside the device body 7. The holding mechanism 18is formed near one edge at the rear side 5 c of the disk tray 5, andincludes a forcing mechanism 19 to force the disk tray 5 to outside thedevice body 7 and an engagement mechanism 20 which engages the disk tray5 into the device body 7.

First, the above forcing mechanism 19 which forces the disk tray 5 tooutside the device body 7 will be explained.

As shown in FIG. 17, the forcing mechanism 19 uses a coil spring 28provided at the rear side 5 c of the disk tray 5 to force out the disktray 5 from inside the device body 7. The coil spring 28 is housed in aspring compartment 29 formed near one of the guide projections 22 toextend in the direction in which the disk tray 5 is inserted into, andejected to outside, the device body 7. The coil spring 28 has a hollowstructure in which a bar-like ejection member 30 is inserted. Theejection member 30 can be inserted in insertion holes 29 b formed inwalls 29 a at the front end 5 a and rear end 5 d, respectively, of thespring compartment 29. Also, the ejection member 30 has a flange 30 aformed generally at the middle of the length thereof. When the flange 30a is pressed at one side thereof by the end of the coil spring 28, theejection member 30 is forced to the rear end 5 d and the flange 30 a isretained at the other side thereof by a step 29 c formed at the rear end5 d of the spring compartment 29. At this time, a portion of theejection member 30, extending from the flange 30 a toward the rear end 5d, is projected to the device body 7 through the insertion hole 29 bformed in the wall 29 a of the spring compartment 29.

When the disk tray 5 is inserted into the device body 7, the portion,projecting toward the device body 7, of the ejection member 30 abuts therear wall 9 a of the lower half 9. As the disk tray 5 is furtherinserted, the ejection member 30 is forced back from the rear wall 9 aand moves toward the front end 5 a and compresses the coil spring 28 bythe flange 30 a toward the rear end 5 a, as shown in FIG. 18. Since thecoil spring 28 is retained at an end thereof at the front end 5 a by thewall 29 a of the spring compartment 29 at this time, it is compressed bythe flange 30 a and the force for pressing the flange 30 a toward therear end 5 d is maintained. Thereafter, when the disk tray 5 is heldengaged inside the device body 7 by the engagement mechanism 20 providedon the disk tray 5, the coil spring 28 holds the force for pressing theflange 30 a toward the rear end 5 d. The engagement mechanism 20 will bedescribed in detail later.

When the disk tray 5 is disengaged by the engagement mechanism 20 afterthe above, the ejection member 30 pressed by the coil spring 28 receivesa reaction equivalent to the force of the coil spring 28 from the rearwall 9 a and presses the coil spring 28 by the flange 30 a back to thefront end 5 a. Since the end, at the front end 5 a, of the coil spring28 is retained by the wall 29 a of the coil compartment 29, the coilspring 28 is decompressed while pressing the wall 29 a toward the frontend 5 a. Thus, the disk tray 5 is pressed out toward the open end of thedevice body 7, the front end 5 a, of the disk tray 5 is projected towardthe open end of the device body 7. The disk tray 5 can thus be drawnout. It should be noted that since the ejection member 30 is forced atthe flange 30 a by the coil spring 28 toward the rear end 5 d, aportion, extending from the flange 30 a toward the rear end 5 d, of theejection member 30 is projected through the insertion hole 29 b formedin the wall 29 a of the spring compartment 29 toward the device body 7as shown in FIG. 16.

Next, the engagement mechanism 20 for engagement of the disk tray 5 intothe device body 7 will be explained below. As shown in FIGS. 17 to 20,the engagement mechanism 20 includes an engagement projection 11provided on the device body 7 to engage with the disk tray 5 and keepthe disk tray 5 engaged in the device body 7, an engagement piece 41provided on the disk tray 5 and forced to pivot in a direction ofengaging the engagement projection 11 with the disk tray 5, a pivotingpiece 42 for engaging the engagement piece 41 onto the engagementprojection 11 or disengaging it from the engagement projection 11 byhaving a contact with the engagement piece 41 and limiting the pivotingrange of the engagement piece 41, a plunger 45 engaging with thepivoting piece 42 and inserted into an on-core coil 44 to pivot thepivoting piece 42, and a pressing piece 46 pressed by the engagementprojection 11 to have a contact with the pivoting piece 42 and press thepivoting piece 42 in a direction in which the engagement piece 41 willengage with the engagement projection 11.

As shown in FIG. 15, the engagement projection 11 is provided on theaforementioned lower half 9 and projected to near the open end of theguide rail 12. The engagement projection 11 is formed generallycylindrical. When the disk tray 5 is inserted into the device body 7,the engagement projection 11 is engaged on an engagement piece 41 formedon the disk tray 5 to hold the disk tray 5 inside the device body 7.

As shown in FIG. 19, the engagement piece 41 engaged on the engagementprojection 11 includes an engagement portion 48 shaped like a hook andengaged on the engagement projection 11, a body 49 having the engagementportion 48 formed at the free end thereof, a stud 50 provided at thebase end of the body 49 to work as a pivot for the engagement piece 41,and an abutting portion 51 put into contact with the pivoting piece 42which will be described in detail later. The engagement piece 41 isshaped to be pivotable about the stud 50 in the direction of arrow D inFIG. 19 or in a direction opposite to the direction of arrow D, and atorsion coil spring 52 is wound on the stud 50 to always force theengagement piece 41 for pivoting in the direction of arrow D in FIG. 19.

The engagement piece 41 has a bevel 49 a formed thereon to protrude fromthe end of the body 49 in the moving direction of the engagementprojection 11 in the direction of arrow D, and the hook-shapedengagement portion 48 is formed at the protruding end of the bevel 49 a.Also, the engagement piece 41 has the abutting portion 51 formed at theside thereof opposite to the side where the bevel 49 a is formed.Namely, the stud 50 is located between the abutting portion 51 and bevel49 a. Since the abutting portion 51 is pressed to abut the pivotingpiece 42, the range of the pivoting in the direction of arrow D in FIG.19 is limited. As pivoted in the direction of arrow D, the engagementportion 48 is engaged on the engagement projection 11, holds the disktray 5 inside the device body 7. On contrary, when pivoted in thedirection opposite to the direction of arrow D in FIG. 19, theengagement portion 48 is disengaged from the engagement projection 11 toenable the disk tray 5 to be ejected from inside the device body 7 bythe aforementioned coil spring 28 and ejection member 30.

The pivoting piece 42 to limit the pivoting range of the engagementpiece 41 includes a pivoting-range limiting projection 55 which pressesthe abutting portion 51 of the engagement piece 41 to limit the pivotingrange, a stud 56 as a pivot for the pivoting piece 42, a contact portion57 which is put into contact with the pressing piece 46 and pressed bythe latter, and a connection 58 connected with the plunger 45.

The pivoting piece 42 is shaped to be pivotable about the stud 56 in thedirection of arrow E in FIG. 19 or in a direction opposite to thedirection of arrow E, and a torsion coil spring 59 is wound on the stud56 to always force the pivoting piece 42 for pivoting in the directionof arrow E in FIG. 19.

As the engagement piece 41 is forced in the direction of arrow D in FIG.19, thus always kept in contact with the abutting portion 51 and pivotedin either the direction of arrow E or in the direction opposite to thedirection of arrow E, the pivoting-range limiting projection 55 limitsthe pivoting range of the engagement piece 41 by means of the abuttingportion 51.

The contact portion 57 has a protrusion 60 formed at a contact thereofwith the pressing piece 46. The protrusion 60 is pressed by the pressingpiece 46 to pivot the pivoting piece 42 in the direction opposite to thedirection of arrow E.

The connection 58 to which the plunger 45 is connected has formed at oneside thereof a projection 58 a inserted through a connection hole 45 aformed in the plunger 45. When the pivoting piece 42 is pivoted by thepressing piece 46 in the direction opposite to the direction of arrow E,the connection 58 moves the plunger 45 toward the on-core coil 44. Whenthe plunger 45 is held inside the on-core coil 44, the pivoting piece 42is held directed in the direction opposite to the direction of arrow E.

Also, a slit 61 is formed between the contact portion 57 and connection58 to permit the contact portion 57 pressed by the pressing piece 46 tobe elastically movable. Therefore, the protrusion 60 formed on thecontact portion 57 permits the pressing piece 46 to positively pivot thepivoting piece 42 and the pivoting piece 42 to hold the plunger 45 inthe on-core coil 44, and the slit 61 can absorb the pressure bydeflecting the contact portion 57 when the contact portion 57 isexcessively pressed by the pressing piece 46.

Forced by the torsion coil spring 59 in the direction of arrow E in FIG.19, the pivoting piece 42 pivots the pivoting-range limiting projection55 put in contact with the abutting portion 51 of the engagement piece41 in the direction of arrow E to pivot the engagement piece 41 in thedirection opposite to the direction of arrow D. Thus, the engagementportion 48 of the engagement piece 41 is disengaged from the engagementprojection 11 provided upright on the lower half 9 of the device body 7,and the disk tray 5 is ejected to outside the device body 7.

Also, when the disk tray 5 is inserted into the device body 7 and thecontact portion 57 is pressed by the pressing piece 46 which will bedescribed in detail later, the pivoting piece 42 is pivoted in thedirection opposite to the direction of arrow E. When the plunger 45connected to the contact portion 57 is held inside the on-core coil 44,the pivoting-range limiting projection 55 is pivoted in the directionopposite to the direction of arrow E to pivot the engagement piece 41 inthe direction of arrow D in FIG. 20. Thus, the engagement portion 48 ofthe engagement piece 41 is engaged on the engagement projection 11 andthe disk tray 5 is held inside the device body 7.

The plunger 45 which holds the pivoting piece 42 directed in thedirection opposite to the direction of arrow E is a generally U-shapedmagnetic member. It has a pair of insertion shafts 63 which are to beinserted into the on-core coil 44, and has a connection hole 45 a formedin the base-end portion thereof. With the projection 58 a formed on theconnection 58 of the pivoting piece 42 being inserted into theconnection hole 45 a, the plunger 45 is connected to the pivoting piece42.

The on-core coil 44 in which the insertion shaft 63 of the plunger 45 ispassed has a coil 66 wound on a hollow core 65 in which the insertionshaft 63 is inserted. Also, the on-core coil 44 incorporates a magnet(not shown) which magnetically attracts the insertion shaft 63 away fromthe inserted end of the insertion shaft 63 in the direction of arrow Fin FIG. 19. When the pivoting piece 42 is pivoted in the directionopposite to the direction of arrow E and the insertion shaft 63 of theplunger 45 is inserted deeper into the on-core coil 44, the insertionshaft 63 is held by the magnet in the on-core coil 44 as shown in FIG.20. Also, when a current is supplied to the coil 66, the on-core coil 44will cancel the magnetic force of the magnet magnetically attracting theinsertion shaft 63 to free the plunger 45. When the plunger 45 is thusfreed, the pivoting piece 42 is pivotable under the force of the torsioncoil spring 59 in the direction of arrow E.

The pressing piece 46 which abuts the contact portion 57 of the pivotingpiece 42 to press the latter includes an arm portion 70 which is pressedby the engagement projection 11 provided upright on the device body 7, astud 71 provided at the base end of the arm portion 70 and about whichthe pressing piece 46 is pivoted, and a pressing portion 72 whichpresses the contact portion 57 of the pivoting piece 42 to pivot thelatter.

The pressing piece 46 is formed to be pivotable about the stud 71 in thedirection of arrow G or in a direction opposite to the direction ofarrow G in FIG. 19, and a torsion coil spring 73 is wound on the stud 71to hold the pressing piece 46 in a position where the arm portion 70intersects the moving orbit of the engagement projection 11 as shown inFIG. 19. That is, the pressing piece 46 is returned by the torsion coilspring 73 to the home position after the arm portion 70 is pressed bythe engagement projection 11 and thus pivoted in the direction of arrowG to pivot the pivoting piece 42 in the direction opposite to thedirection of arrow E or even when the contact portion 57 collides withthe pivoting piece 42 having been pivoted in the direction of arrow E tocause the pivoting piece 42 to pivot in the direction opposite to thedirection of arrow G.

The torsion coil spring 73 to limit the position of the pressing piece46 is wound on the stud 71 and has one end thereof retained by thepressing piece 46 and at the other end by a retaining member 75 formedon the rear side 5 c of the disk tray 5. The retaining member 75consists of a semi-circular retention piece 75 a and a rectangularretention piece 75 b between which a constant clearance is defined. Thetorsion coil spring 73 is inserted at the other end thereof into theclearance and wound on the semi-circular retention piece 75 a. Since theretention piece 75 a is formed semi-circular while the retention piece75 b is formed rectangular, the torsion coil spring 73 cannot be woundon the retention piece 75 b but is only wound on the semi-circularretention piece 75 a. Therefore, the torsion coil spring 73 applies anoptimum force to the pressing piece 46, so than the pressing piece 46once pressed by the engagement projection 11 and pivoting piece 42 topivot in the direction of arrow G or in the direction opposite to thedirection of arrow G can be return to the home position where the armportion 70 intersects the moving orbit of the engagement projection 11.

Note that in a position near the area where the arm portion 70 ispivoted and at a side opposite to the direction of arrow G and, there isprovided a stopper 80 which stops the arm portion 70 from beingexcessively pivoted. The stopper 80 is a cylindrical projection, forexample, provided on the rear side 5 c of the disk tray 5. When thecontact portion 57 of the pivoting piece 42 pivoted in the direction ofarrow E collides with the pressing piece 46 which will thus be pivotedin the direction opposite to the direction of arrow G, the arm portion70 is limited by the stopper 80 from being excessively pivoted in thedirection opposite to the direction of arrow G as shown with a dashedline in FIG. 19. Thus, the pressing piece 46 assures that the armportion 70 can be back to the moving orbit of the engagement projection11.

More specifically, on the assumption that the arm portion 70 will notreturn to the moving orbit of the engagement projection 11, the latterwill not allow the arm portion 70 when the disk tray 5 is inserted intothe device body 7. Thus, the pressing piece 46 cannot pivot the pivotingpiece 42 in the direction of arrow E and the engagement piece 41 cannotbe pivoted in the direction of arrow D to engage onto the engagementprojection 11. Thus, the arm portion 70 of the pressing piece 46 has thepivoting range thereof limited by the stopper 80 provided to assure thatthe arm portion 70 can be back to the moving orbit of the engagementprojection 11 without fail.

In the engagement mechanism 20 including the engagement projection 11,engagement piece 41, pivoting piece 42, plunger 45 and pressing piece 46as mentioned above, when the disk tray 5 is outside the device body 7,the pivoting piece 42 is forced in the direction of arrow E, retained bya stop wall 81 provided on the disk tray 5 and thus limited frompivoting in the direction of arrow E as shown in FIG. 19. Also, theengagement piece 41 has the abutting portion 51 thereof pivoted by thepivoting-range limiting projection 55 of the pivoting piece 42 in thedirection opposite to the direction of arrow D and the engagementportion 48 thereof kept in a position where it is retracted from themoving orbit of the engagement projection 11. Therefore, the lower half9 of the device body 7 having the engagement projection 11 providedupright thereon and the disk tray 5 are disengaged from each other, therear wall 9 a of the lower half 9 is forced by the ejection member 30forced by the coil spring 28 provided on the disk tray 5, and thus thedisk tray 5 is ejected to outside the device body 7.

When the user inserts the disk tray 5 into the device body 7 with anoptical disk 4 set in place in the concavity 15 of the disk tray 5, theengagement projection 11 provided on the lower half 9 goes forward inthe direction of arrow H in FIG. 19 and gets in touch with the armportion 70 of the pressing piece 46. Thus the arm portion 70 is pivotedin the direction of arrow G in FIG. 20. As the arm portion 70 is thuspivoted, the pressing portion 72 of the pressing piece 46 presses thecontact portion 57 of the pivoting piece 42 which will thus be pivotedin the direction opposite to the direction of arrow E in FIG. 20. Thus,the plunger 45 connected to the connection 58 of the pivoting piece 42will have the insertion shaft 63 inserted deep into the on-core coil 44and magnetically attracted by the magnet disposed inside the on-corecoil 44.

At this time, the pressing piece 46 presses the protrusion 60 formed onthe contact portion 57 that gets into touch with the pressing portion 72of the pressing piece 46 to positively pivot the pivoting piece 42 inthe direction opposite to the direction of arrow E, so that the plunger45 can be magnetically attracted by the magnet disposed inside theon-core coil 44. Also, the slit 61 formed between the contact portion 57and connection 58 of the pivoting piece 42 allows the contact portion 57to elastically be displaceable. Therefore, when excessively pressed bythe pressing piece 46, the contact portion 57 can be deflected to absorbthe excessive pressure.

Thus, the plunger 45 and pivoting piece 42 are kept pivoted in thedirection opposite to the direction of arrow E in FIG. 20 against theforce of the torsion coil spring 59 given in the direction of arrow E inFIG. 20. When the pivoting-range limiting projection 55 of the pivotingpiece 42 is pivoted in the direction opposite to the direction of arrowE, the engagement piece 41 has the pivoting range thereof increased inthe direction of arrow D and the force of the torsion coil spring 52given in the direction of arrow D in FIG. 20 positions the engagementportion 48 on the moving orbit of the engagement projection 11 as shownin FIG. 20.

As the disk tray 5 is inserted deeper in the device body 7, theengagement projection 11 goes forward in the direction of arrow H inFIG. 20 while pivoting the bevel 49 a on the free end portion of thebody 49 of the engagement piece 41 in the direction opposite to thedirection of arrow D, and is engaged on the engagement portion 48. Thus,the disk tray 5 and the lower half 9 of the device body 7 engage witheach other.

At this time, the ejection member 30 is pressed back from the rear wall9 a of the lower half 9 and moves toward the front end 5 a whilecompressing the coil spring 28 by the flange 30 a thereof toward thefront end 5 a, as shown in FIG. 18. Since the coil spring 28 has the endthereof at the front end 5 a retained by the wall 29 a of the springcompartment 29, it is pressed by the flange 30 a and thus compressed tokeep a force under which the flange 30 a is forced toward the rear end 5d. That is, the disk tray 5 is held in place inside the device body 7while forcing the lower half 9 toward the rear end 5 d to engage theengagement piece 41 on the engagement projection 11 provided on thelower half 9.

To eject the disk tray 5 from inside the device body 7, the controlcircuit supplied with a command signal from a user's control unitprovided on the disk tray 5 supplies a current to the on-core coil 44 tocancel the magnetic force of the magnet built in the on-core coil 44.Thus the plunger 45 is freed. Therefore, the pivoting piece 42 ispivoted in the direction opposite to the direction of arrow E in FIG. 19under the force of the torsion coil spring 59. When the pivoting-rangelimiting projection 55 is pivoted in the direction of arrow E, theengagement piece 41 is pivoted in the direction opposite to thedirection of arrow D and has the engagement portion 48 thereof retractedfrom on the moving orbit of the engagement projection 11. Thus, theengagement projection 11 is disengaged from the engagement portion 48,so that the disk tray and the lower half 9 of the device body 7 will bedisengaged from each other.

Then, the ejection member 30 having the free end thereof thrust upon therear wall 9 a of the lower half 9 is given a reaction equivalent to theforce of the coil spring 28 from the rear wall 9 a, and thus forces backthe coil spring 28 by the flange 30 a toward the front end 5 a. Sincethe coil spring 28 has the end thereof at the front end 5 a retained bythe wall 29 a of the coil compartment 29, it is decompressed whilepressing the compartment wall 29 a toward the front end 5 a. Thus, thedisk tray 5 is pressed out toward the open end of the device body 7 andthus has the front end 5 a thereof ejected toward the open end of thedevice body 7.

Note that since the arm portion 70 is retained by the stopper 80 alsowhen pivoting of the pivoting piece 42 in the direction of arrow E hascaused the pressing portion 72 of the pressing piece 46 to collide withthe contact portion 57 of the pivoting piece 42 and thus pivoted thepressing portion 72 in the direction opposite to the direction of arrowG, it can be avoided that the arm portion 70 will excessively be pivotedand not be positioned on the moving orbit of the engagement projection11. Also, the torsion coil spring 73 wound on the pressing piece 46 canbe retained in an appropriate position by the retaining member 75 formedon the rear side 5 c of the disk tray 5 and thus provides an optimumforce to the pressing piece 46. Therefore, even when having been pressedby the engagement projection 11 and pivoting piece 42 and pivoted in thedirection of arrow G or in the direction opposite to the direction ofarrow G, the pressing piece 46 is returned to the initial position wherethe arm portion position 70 intersects the moving orbit of theengagement projection 11 as indicated with a solid line in FIG. 19.

Note that the protrusion 60 formed on the contact portion 57 of thepivoting piece 42 as above may be formed on the pressing portion 72 ofthe pressing piece 46 or on both the pivoting piece 42 or pressing piece46.

Next, the optical pickup unit 6 installed in the compartment 21 providedat the rear side 5 c of the disk tray 5 will be explained.

As shown in FIG. 21, the optical pickup unit 6 includes a base chassis101 forming the unit body, a disk table 102 formed integrally with thebase chassis 101 and on which an optical disk 4 is placed, an opticalpickup 103 to write or read information signals to or from the opticaldisk 4 placed in place on the disk table 102, a pickup moving mechanism104 to move the optical pickup 103 radially of the optical disk 4, apair of guide shafts 105 and 106 to guide the movement of the opticalpickup 103 by the pickup moving mechanism 104, and a skew adjustingmechanism 109 to adjust the relation in inclination between an objectivelens 108 provided on the optical pickup 103 and the signal recordingsurface of the optical disk 4 by adjusting the inclination of the guideshafts 105 and 106.

The base chassis 101 includes an iron-made frame 110. The frame 110 isformed generally rectangular, and has an opening 112 through which theobjective lens 108 of the optical pickup 103 faces directly the signalrecording surface of the optical disk 4. The opening 112 is formedgenerally rectangular. In the opening 112, there are disposed the pickupmoving mechanism 104 to move the optical pickup 103 longitudinally, pairof guide shafts 105 and 106 and the optical pickup 103 supported on theguide shafts 105 and 106. The opening 112 has a generally circular cut113 formed at one longitudinal end thereof. Also, the circular disktable 102 on which an optical disk 4 is placed and a spindle motor (notshown) to drive the rotation of the disk table 102 are disposed in theopening 112.

The frame 110 has a plurality of engagement holes 111 through which thebase chassis 101 is engaged on a plurality of engagement projections 25provided in the compartment 21 formed on the rear side 5 c of the disktray 5. With the engagement projections 25 being engaged in thecorresponding engagement holes 111, the frame 110 is housed in thecompartment 21.

As shown, the optical pickup 103 to write or read information signals toor from the optical disk 4 placed on the disk table 102 includes apickup base 114 formed from a generally rectangular case. On this pickupbase 114, there are disposed at least a light source (not shown) such asa semiconductor laser or the like, objective lens 108 to focus a lightbeam emitted from the light source onto the signal recording surface ofthe optical disk 4, photodetector (not shown) to detect a return lightfrom the recording surface of the optical disk 4, and a drive systemwhich moves the objective lens 108 in directions of focusing andtracking the optical disk 4. Also, the optical pickup 103 has formed ina longitudinal one end 114 a of the pickup base 114 an insertion hole116 in which the guide shaft 105 is inserted, and formed at the otherend 114 b thereof an engagement piece 117 which engages on the guideshaft 106. The guide shafts 105 and 106 will be described in detaillater. The pickup base 114 has installed thereon a flexible printedwiring board 119 having formed thereon a drive circuit for controllingthe drive system for the objective lens 108 and the like.

Also, the optical pickup 103 has formed thereon an engagement member 120provided adjacent to the guide shaft 105 and which engages with a leadscrew 140 of the pickup moving mechanism 104 which moves the pickup base114.

Supported on the pair of guide shafts 105 and 106 disposed alongopposite edges, respectively, of the opening 112 in the base chassis101, the optical pickup 103 is guided by the guide shafts 105 and 106 inmoving between the inner and outer circumferences of the optical disk 4,and has the objective lens 108 thereof exposed the signal recordingsurface of the optical disk 4 through the opening 112.

The guide shafts 105 and 106 in pair to guide the movement of theoptical pickup 103 are disposed opposite to the opening 112 in the basechassis 101. The guide shaft 105 (106) is thinner at opposite endsthereof than the main portion. The end-portion diameter of the guideshaft 105 (106) is about 1.2 mm, for example. The guide shaft 105 (106)is supported at the opposite ends thereof by the skew adjustingmechanism 109 which adjusts the vertical inclination of the guide shafts105 and 106. The guide shafts 105 and 106 are formed from anelectroconductive material. Since an adjusting screw used with eachguide shaft is formed also from an electrically conductive material,grounding of the adjusting screw makes it possible to remove the chargeon the guide shafts 105 and 106.

As shown in FIG. 21, the skew adjusting mechanism 109 is provided atfour places correspondingly opposite ends of the pair of guide shafts105 and 106. As will be seen in FIG. 22, the skew adjusting mechanism109 includes a housing 125 provided inside the base chassis 101, anelastic member 126 provided inside the housing 125 to force the guideshafts 105 and 106, and an adjusting screw 127 provided at a sideopposite to the elastic member 126 across the guide shaft 105 (106) topress the guide shaft 105 (106) from a side opposite to the elasticmember 126.

The housing 125 is disposed between the upper and lower sides 101 a and101 b of the base chassis 101. Also, the housing 125 has formed thereinan insertion hole 128 in which one end of the guide shaft 105 (106) isinserted. In the housing 125, there is housed the elastic member 126which forces the guide shafts 105 and 106. The adjusting screw 127inserted in a screw hole 129 formed in the lower side 101 b of the basechassis 101 is exposed inside the housing 125.

The elastic member 126 is a helical spring formed generally conical, forexample. The elastic member 126 is disposed to have a smaller-diameterend 126 a thereof put in contact with the upper surface of the guideshaft 105 (106) and a larger-diameter base end 126 b thereof put incontact with the upper wall of the housing 125.

When the guide shaft 105 (106) is pressed by the adjusting screw 127,the elastic member 126 is pinched and thus compressed between the guideshaft 105 (106) and the inner wall of the housing 125. At this time, theelastic member 126 is compressed to a length of 1 mm or less while thesmaller-diameter end 126 a thereof abutting the guide shaft 105 (106) ismoved to inside the larger-diameter base end 126 b. Therefore, theelastic member 126 used in the present invention can be compressed to areduced length as compared with a cylindrical elastic member whose canbe compressed to a length of 1 mm or more. Thus, the housing 125 as awhole can be designed to have a reduced thickness, for example, to athickness of about 4 mm, and the base chassis 101 can be designedthinner.

Also, the adjusting screw 127 is inserted in the screw hole 129 formedin the lower side 101 b of the base chassis 101 and has the free endthereof put in contact with the lower side of the guide shaft 105 (106).By adjusting the length of projection of the adjusting screw 127 intothe housing 125, the inclination of the guide shafts 105 and 106 can beadjusted in steps of ±0.4 mm for example.

Note that the adjusting screw 127 is nickel- or copper-plated to beelectroconductive. The adjusting screw 127 works also as a groundingconductor for the guide shaft 105 (106) because it connects to the lowerside 101 b, at the ground potential, of the base chassis 101 and abutsthe lower surface of the guide shaft 105 (106).

The above skew adjusting mechanism 109 is provided at four placescorrespondingly to the opposite ends of each of the guide shafts 105 and106. During assembling of the optical pickup unit 6, the skew adjustingmechanism 109 of the skew adjusting mechanism 109 is used with askew-adjustment disk to adjust the inclination of the guide shafts 105and 106 so that a light beam projected from the objective lens 108 isincident perpendicularly upon the signal recording surface of theskew-adjustment disk, and thus the relation in inclination between theobjective lens 108 and signal recording surface of the skew-adjustmentdisk.

After completion of the skew adjustment with the skew adjustingmechanism 109, the elastic member 126 may be fixed with an adhesive toprevent the skew angle from varying. That is, the skew adjustingmechanism 109 has adhesive-injection holes 131 and 132 formed in theupper side 101 a of the base chassis 101 and housing 125 as shown inFIG. 23. The adhesive-injection holes 131 and 132 are formed inpositions corresponding to the locations of the elastic members 126. Anadhesive 133 of ultraviolet setting type, for example, is injected intothe adhesive-injection holes 131 and 132.

During assembling of the optical pickup unit 6, the adjusting screw 127of the skew adjusting mechanism 109 is used to adjust the inclination ofthe guide shafts 105 and 106 and then inject the adhesive 133 from theadhesive-injection holes 131 and 132 in order to harden the elasticmember 126. Thus, since the elastic member 126 can be hardened with theadhesive 133, the skew adjusting mechanism 109 can maintain anappropriate inclination of the guide shafts 105 and 106 even if theelastic member 126 is plastically be deformed due to the compression.

Note that the adhesive-injection holes 131 and 132 formed in the basechassis 101 and housing 125 are very small in diameter and so anadhesive 133 in liquid condition injected through them will not spillout of the base chassis 101 owing to its surface tension.

Also, the skew adjusting mechanism 109 uses a conical helical spring asthe elastic member 126, but it may use a hollow cylinder of siliconrubber instead as shown in FIG. 24. The silicon-rubber hollow cylinderis disposed to have one end thereof in touch with the upper side of theguide shaft 105 (106) as well as the other end thereof in contact withthe inner wall of the housing 125.

As the guide shafts 105 and 106 are pressed by the adjusting screw 127,the elastic member 126 of silicon rubber is compressed between the guideshaft 105 (106) and inner wall of the housing 125. At this time, theelastic member 126 is compressed by reducing the volume of the partthereof compressed inside the elastic member 126. Also, the elasticmember 126 may be hardened with the adhesive 133 of ultraviolet settingtype injected through the adhesive-injection holes 131 and 132 aftercompletion of the skew adjustment. Thus, since the elastic member 126 ishardened with the adhesive 133, the skew adjusting mechanism 109 canmaintain the appropriate inclination of the guide shafts 105 and 106even if the elastic member 126 is plastically deformed due to thecompression by the adjusting screw 127.

Note that the guide shafts 105 and 106 may be used also as a groundingconductor by adding an additive to the elastic member 126 of siliconrubber to render the elastic member 126 electroconductive whileconnecting the elastic member 126 to the lower side 101 b, at the groundpotential, of the base chassis 101 and putting it into contact with thelower surface of the guide shaft 105 (106).

In the above skew adjusting mechanism 109, the housing 125 in which theelastic member 126 and adjusting screw 127 are disposed is held betweenthe upper and lower sides 101 a and 101 b of the base chassis 101. So,the space for installation of the elastic member 126 can be made flat,which leads to a thinner design and simpler process of manufacture ofthe base chassis 101 as compared with the conventional base chassis inwhich supports for the guide shafts of the skew adjusting mechanism areformed by deep drawing.

The pickup moving mechanism 104 to move the optical pickup 103 radiallyof the optical disk 4 is provided adjacent to the guide shaft 105. Asshown in FIGS. 21 and 25, the pickup moving mechanism 104 includes thelead screw 140 installed to the base chassis 101 adjacent and inparallel to the guide shaft 105 along the radius of the optical disk 4,and a feed motor 141 to rotate the lead screw 140.

The lead screw 140 is supported at the end of a shaft portion 140 athereof in a bearing 143 to be rotatable. The shaft portion 140 a of thelead screw 140 has formed thereon threads 144 which are engaged slidablyon the engagement member 120 provided on the pickup base 114. As rotatedby the feed motor 141, the lead screw 140 can move the pickup base 114radially of the optical disk 4 by means of the engagement member 120.

The feed motor 141 to rotate the lead screw 140 is a DC motor which isconstructed as a step motor. Supplied with a rectangular wave, the feedmotor 141 runs stepwise to rotate the lead screw 140 for moving thepickup base 114 radially of the optical disk 4.

The feed motor 141 to rotate the lead screw 140 is a DC motor. Since theDC motor will not provide any torque unless it runs at a high speed,various contact portions of the pickup moving mechanism 104 will heavilybe abraded. Also, in case the feed motor is connected via a gearmechanism to the lead screw 140 to move the pickup base 114, it willemit a large operating noise.

On this account, the feed motor 141 in the present invention uses a stepmotor. Supplied with a rectangular-wave pulse, the feed motor 141 movesthe pickup base 114 radially of the optical disk 4.

As shown in FIGS. 25A and 25B, the feed motor 141 has a motor housing145 which has no upper and lower walls. The motor housing 145 has formedtherein openings 142 through which a coil 146 housed inside is exposedto outside from the upper and lower sides of the motor housing 145.Because of the openings 142 with no upper and lower walls, the motorhousing 145 is formed thinner for the thickness of the wall, forexample, to a thickness of 5.1 mm.

The feed motor 141 and lead screw 140 are installed to a frame 148 andfurther to the base chassis 101 with the frame 148 between them. Theframe 148 includes a generally rectangular plate-shaped connection 148 ahaving connected thereto a side portion of the motor housing 145 fromwhich the lead screw 140 is projected out and the bearing 143 supportingthe end of the lead screw 140, and a fixing side portion 148 b formedfrom a bent part of the connection 148 a and having formed therein abinding-screw hole 149 in which a binding screw for fixation to the basechassis 101 is inserted.

The pickup moving mechanism 104 constructed as above can be installed byfixing, with binding screws, the frame 148 having the lead screw 140 andfeed motor 141 installed thereto in place on the base chassis 101 asshown in FIG. 25.

In the pickup moving mechanism 104 in which the frame 148 is fixed tothe base chassis 101, when the base chassis 101 is held between thecover member 90 covering the optical pickup unit 6 which will bedescribed in detail later from above and a bottom plate 91 covering theoptical pickup unit 6 from above, the openings 142 formed in the upperand lower sides of the motor housing 145 are closed by the cover member90 and bottom plate 91, as shown in FIG. 29. Thus, the cover member 90and bottom plate 91 can work as a yoke to close the magnetic field ofthe coil 146 housed in the motor housing 145. Thus, it is possible toprevent the fringe magnetic field from the feed motor 141 from adverselyaffecting write or read of information signals to or from the opticaldisk 4 as well as to prevent any foreign matter such as dust or the likefrom entering the motor housing 145. It should be noted that theopenings 142 in the motor housing 145 can fully be closed by the covermember 90 and bottom plate 91 and some gap possibly taking place betweenthe cover member 90 and bottom plate 91 due to the dimensionaltolerances of various parts may be allowed.

Also, the motor housing 145 for the feed motor 141 is open at the upperand lower sides thereof in the pickup moving mechanism 104, heatdeveloped inside the motor housing 145 can easily be exhausted. Morespecifically, in the pickup moving mechanism 104, when the pickup base114 is moved from a stationary state, the friction coefficient isimportant and thus a large torque is required. Once the pickup base 114is put into movement, however, the friction coefficient will be smallerand the torque is lowered correspondingly. After that, the pickup base114 in the pickup moving mechanism 104 is applied with a sufficienttorque to prevent any displacement of the pickup base 114 (holdingtorque). The holding torque will always be applied during operation ofthe recorder/player 1 and the feed motor 141 is always supplied with acurrent. On this account, the motor housing 145 for the feed motor 141is designed open at the upper and lower sides thereof to prevent thefeed motor 141 from being excessively heated, to thereby prevent theoperation of moving the pickup base 114 from being adversely affected bythe heat dissipated from the feed motor 141.

Also, in the above pickup moving mechanism 104, since the motor housing145 for the feed motor 141 is open at the upper and lower sides thereof,it can be formed thinner than the base chassis 101. Thus, therecorder/player 1 can be designed thinner by limiting the thickness ofthe base chassis 101 having the pickup moving mechanism 104 fixedthereto.

As shown in FIGS. 26 to 28, the engagement member 120 engaging with thethreads 144 formed on the lead screw 140 is fixed at one end thereof tothe pickup base 114 with binding screws and engaged at the other endthereof in the threads 144 on the lead screw 140 to convert the rotarymotion of the lead screw 140 into a linear motion.

The engagement member 120 includes engagement projections 151 which areengaged in the threads 144 formed on the lead screw 140, and acompartment 153 provided contiguously to the pickup base 114 and inwhich there is housed a clearance definition member 152 to keep theengagement projections 151 at a distance over which they are keptengaged on the lead screw 140.

The engagement projections 151 are provided on a side wall 153 a, at theside of the lead screw 140, of the compartment 153 to project toward thelead screw 140. The engagement member 151 is beveled equally to thebevel of the threads 144 on the lead screw 140. Also, the engagementmember 151 is generally as wide as the threads 144.

The engagement projections 151 are engaged in the threads 144 to a depthof the latter, for example, to a depth of 0.3 mm. As the lead screw 140is rotated, the engagement projections 151 are moved along the threads144 axially of the lead screw 140.

The compartment 153 having the engagement projections 151 formed thereonis a concavity whose section is generally C-shaped and open at the topthereof. In the compartment 153, engagement projections 155 and 156 areformed on the side wall 153 a of the lead screw 140 and side wall 153 bof the guide shaft 105, respectively. The engagement projections 155 and156 are provided to prevent the clearance definition member 152 fromexiting from the compartment 153. The clearance definition member 152will be described in detail later.

A connecting surface 157 is formed on the upper edge of the side wall153 b of the guide shaft 105 to connect the engagement member 120 to thepickup base 114. The connecting surface 157 is provided to extend overthe guide shaft 105 disposed between the lead screw 140 and pickup base114 to above the pickup base 114 and is connected with a binding screwto the upper side of the pickup base 114.

The clearance definition member 152 housed in the compartment 153 tosupport the side walls 153 a and 153 b is formed from a rigid, generallyC-shaped metallic plate. As shown in FIG. 27, the clearance definitionmember 152 has slits 158 a and 159 a formed nearly in the center of thesupport walls 158 and 159, respectively. The slits 158 a and 159 aextend vertically from the upper end. With the engagement projections155 and 156 provided on the side walls 153 a and 153 b, respectively,being retained by the slits 158 a and 159 a, the clearance definitionmember 152 is blocked from exiting from the compartment 153.

As shown in FIG. 28, when the clearance definition member 152 is housedin the compartment 153, there are defined between the side walls 153 aand 153 b of the compartment 153 and support walls 158 and 159 of theclearance definition member 152 clearances smaller than the depth ofengagement between the engagement projection 151 and threads 144 on thelead screw 140, for example, a depth of 0.1 mm. Therefore, the clearancedefinition member 152 is housed without forcing the side wall 153 a ofthe compartment 153 toward the lead screw 140. Also, since the clearancedefinition member 152 is rigid as mentioned above, even a misalignmentbetween the engagement projection 151 and threads 144, if any caused dueto the dimensional tolerance of the engagement member 120 duringmovement of the pickup base 114, can be limited to within the clearance(0.1 mm) defined between the side wall 153 a of the compartment 153 andsupport wall 158 of the clearance definition member 152. Thus, theengagement member 120 prevents the engagement projection 151 from beingmisaligned to more than the depth of the threads 144 (0.3 mm) and thelead screw 140 and engagement projection 151 from being disengaged fromeach other during movement of the pickup base 114.

Also, in the recorder/player 1 according to the present invention, theengagement member and the clearance definition member housed in thecompartment of the engagement member may be formed as will be describedbelow. As shown in FIG. 30, an engagement member, generally indicatedwith a reference 220, includes a compartment 222 having formed outsidethereof a pair of engagement projections 221 a and 221 b which areengaged in the threads 144 on the lead screw 140 and in which there ishoused a clearance definition member 223 to keep the engagementprojections 221 a and 221 b in position where they are kept in mesh withthe threads 144 on the lead screw 140, and a connecting surface 225fixed with a binding screw to a part of the pickup base 114 to connectthe compartment to the pickup base 114.

The compartment 222 is a concavity having a generally C-shaped sectionopen at the top thereof. The compartment 222 is formed from a first sidewall 226 at the pickup base 114, a second side wall 227 providedopposite to the first side wall 226 and at the lead screw 140, and apair of compartment walls 228 and 229 rising from the first side wall226, which define together an area in which there is housed a clearancedefinition member 223 which will be described in detail later. The firstand second side walls 226 and 227 have formed thereon inwardly thereofretaining projections 231 and 232, respectively, which will retain theclearance definition member 223 inside the compartment 222.

On the second side wall 227, a pair of engagement projections 221 a and221 b to be engaged in the threads 144 on the lead screw 140 are formedoutwardly with an interval generally equal to that between the threads144 in the extending direction of the shaft portion 140 a of the leadscrew 140. The engagement projections 221 a and 221 b are formedinclined at an angle generally equal to that of the threads 144 on thelead screw 140. The engagement projections 221 a and 221 b are engagedin the threads 144 to the depth of the threads 144, for example, to adepth of 0.3 mm for example. Therefore, when the lead screw 140 isrotated, the engagement projection 221 is moved along the threads 144and axially of the lead screw 140.

Also, the compartment 222 has the compartment walls 228 and 229 formedto overhang to short of the second side wall 227 and the second sidewall 227 has the base end thereof formed thin, and there is thus formeda hinge 233 which allows the second side wall 227 to be deflected towardand away from the lead screw 140. Therefore, the second side wall 227will deflect inwardly of the compartment 222 and thus apply no excessiveload to the lead screw 140 even if the engagement projections 221 a and221 b are pressed to the threads 144 on the lead screw 140 due to thedimensional tolerance of the engagement member 220, vibration of thepickup base 114 during movement or the like. Therefore, it is possibleto assure a smooth rotation of the lead screw 140 and quick movement ofthe pickup base 114.

Also, the compartment 222 has a generally rectangular opening 235 formedon the bottom thereof. Thus, since the second side wall 227 has the baseends of side edges 227 a and 227 b thereof extending along the leadscrew 140 supported by a pair of hinges 233 a and 233 b, respectively,it is assured that the engagement projections 221 a at one edge 227 aand the engagement projection 221 b at the other edge 227 b canseparately be engaged in the threads 144 on the lead screw 140.

On the other hand, in the engagement member in which the pair ofengagement projections 221 a and 221 b are supported only by one hinge,it is assured that the engagement projections 221 a and 221 b in paircan be engaged together on the lead screw 140. Therefore, if thedimensional tolerance of the engagement member 220 or vibration of thepickup base 114 during movement has caused a conflict between theinclination of the threads on the lead screw and that of one of theengagement projections 221 a and 221 b or a strong engagement of theengagement projection in the threads, the other engagement projectionwill not possibly engaged in the threads or will possibly be engaged inthe threads but to a small depth.

In the engagement projection 220 used in the present invention, theedges 227 a and 227 b of the second side wall 227 are supported at thebase ends thereof by the hinges 233 a and 233 b, respectively, and theengagement projections 221 a and 221 b in pair are separately engaged inthe threads 144 on the lead screw 140. Therefore, even if any one of theengagement projections 221 a and 221 b is not well engaged in thethreads 144, the other engagement projection 221 a or 221 b canpositively be engaged in the threads 144 without being influenced by thepoor engagement of the one engagement projection.

The clearance definition member 223 housed in the compartment 222 is arigid, generally C-shaped metallic plate. The clearance definitionmember 223 has formed thereon first and second support walls 237 and 238in pair, each having a size large enough to be housed in the compartment222, to support the second side wall 227 when they are housed in thecompartment 222. The first and second support walls 237 and 238 havevertical slits 237 a and 238 a, respectively, formed generally in thecenter thereon correspondingly to the retaining projections 231 and 232,respectively, formed on the first and second side walls 226 and 227,respectively, formed on the compartment 222. When the clearancedefinition member 223 is housed in the compartment 222, the retainingprojections 231 and 232 formed on the first and second side walls 226and 227, respectively, are retained by the slits 237 a and 238 a andthus prevented from coming out of the compartment 222.

For housing the clearance definition member 223 in the compartment 222,the horizontal length of the first support wall 237 provided at the sideof the pickup base 114 is shorter than the spacing between thecompartment walls 228 and 229 rising from the first side wall 226. Onthe other hand, the second support wall 238 provided at the side of thelead screw 140 has formed thereon right and left support pieces 240extended beyond the first side wall 237 toward the side of thecompartment 222, and it is formed to have a length generally equal to orlarger than that of the horizontal length of the second side wall 227.

When the clearance definition member 223 is housed in the compartment222, there will be defined between the first and second side walls 226and 227 of the compartment 222 and first and second support walls 237and 238 of the clearance definition member 223 clearances shorter thanthe depth of engagement of the engagement projection 221 in the threads144 on the lead screw 140, for example, a depth of 0.1 mm (as shown inFIG. 28). Therefore, the clearance definition member 223 is housed intothe compartment 222 without forcing the second side wall 227 of thecompartment 222 toward the lead screw 140. Also, since the clearancedefinition member 223 is rigid as mentioned above, a misalignmentbetween the engagement projection 221 and the threads 144, if any causedduring movement of the pickup base 114 due to the dimensional toleranceof the engagement member 220, can be limited to within the clearance(0.1 mm) defined between the second side wall 227 of the compartment 222and second support wall 238 of the clearance definition member 223.Thus, the engagement member 220 prevents the engagement projection 221from being misaligned to more than the depth of the threads 144 (0.3 mm)and the lead screw 140 and engagement projection 221 from beingdisengaged from each other during movement of the pickup base 114.

Also, when the clearance definition member 223 is housed in thecompartment 222, the support pieces 240 formed on the second side wall238 can support the second side wall 227 of the compartment 222 over theentire horizontal width as shown in FIGS. 31 and 32. During movement ofthe pickup base 114 or if the recorder/player 1 incorporating theengagement member 220 is dropped by mistake, the clearance definitionmember 223 can relieve the load concentrated to the hinge 233 supportingthe second side wall 227 by the engagement projections 221 a and 221 bengaged in the threads 144 on the lead screw 140.

More specifically, the engagement member 220 has the hinge 233 formed byreducing the thickness of the base end of the second side wall 227 forthe latter to be flexible toward and away from the lead screw 140. Ifthe recorder/player 1 is dropped by mistake and the pickup base 114quickly slides on the guide shafts 105 and 106, the engagement member220 installed on the pickup base 114 will quickly slide on the leadscrew 140. In this case, a dropping impact of the pickup base 114 willconcentrate, via the pair of engagement projections 221 a and 221 bengaged in the threads 144 on the lead screw 140, to the hinge 233supporting the second side wall 227 having the engagement projections221 a and 221 b provided thereon. The dropping impact will distort thesecond side wall 227, especially, the right and left edges 227 a and 227b of the second side wall 227, in the direction of arrow I or J in FIG.32, somewhat deviated from the appropriate direction of deflection. Thedeflection of the edges 227 a and 227 b of the second side wall 227 in adistorted form will cause an excessive load to the hinge 233 which willpossibly be broken.

However, in the recorder/player 1 according to the present invention,the second support wall 238 of the clearance definition member 223 hasprovided thereon the support pieces 240 to support the edges 227 a and227 b of the second side wall 227. So, even if a load in the directionof arrow I or J in FIG. 32 is applied to the edges 227 a and 227 b ofthe second side wall 227 when the recorder/player 1 is dropped, thesupport pieces 240 of the clearance definition member 223 will supportthe second side wall 227 and thus relieve the load to the hinge 223,thus permitting to prevent the hinge 223 from being broken.

Also, the clearance definition member may be formed similarly to theaforementioned clearance definition member 223 by bending the free endof the support piece toward the second side wall 227 as shown in FIG.33. This clearance definition member, indicated with a reference number250, is shaped to have a generally C-shaped section similarly to theaforementioned clearance definition member 223, and has formed thereonfirst and second support walls 251 and 252 in pair to support first andsecond side walls formed on the compartment 222. The first and secondsupport walls 251 and 252 have formed nearly in the center thereof slits251 a and 252 a, respectively, corresponding to engagement projections231 and 232 formed on the first and second side walls 226 and 227,respectively, of the compartment 222. The slits 251 a and 252 a extendvertically from the upper end.

Also, in the clearance definition member 250, the horizontal length ofthe first support wall 251 is smaller than the spacing between thecompartment walls 228 and 229 provided to rise from the first side wall226. On the other hand, the second support wall 252 has right and leftsupport pieces 253 formed to extend beyond the first support wall 251toward the compartment 222, and has a length generally equal to orlarger than the horizontal length of the second side wall 227.

These support pieces 253 have formed at the right and left ends thereoffolds 254 bent toward the second side wall 227. When the clearancedefinition member 250 is housed in the compartment 222, the folds 254extend toward the second side wall 227 and hold the opposite ends 227 aand 227 b of the second side wall 227 between them as shown in FIGS. 34and 35.

Similarly to the aforementioned clearance definition member 223, theabove clearance definition member 250 will work as follows. It isassumed here that the recorder/player 1 is dropped by mistake, thepickup base 114 will quickly slide on the guide shafts 105 and 106 andas dropping impact is applied in the direction of arrow K or in thedirection of arrow L in FIG. 35, somewhat deviated from the appropriatedirection of distortion. In this case, the right end 227 a or left end227 b of the second side wall 227 of the engagement member 220 will besupported by the support piece 253. Also, even if the pickup base 114quickly slides and a load is applied in the direction of arrow M or inthe direction opposite to the direction of arrow M in FIG. 35 in whichthe pickup base slides, the edges 227 a and 227 b of the second sidewall 227 will be supported by the folds 254 formed at the free end ofthe support piece 253. Therefore, the lead to the hinges 233 a and 223 bsupporting the edges 227 a and 227 b of the second side wall 227 isrelieved and the engagement member 220 is prevented from being broken.

Note that similarly to the aforementioned clearance definition member152, the above clearance definition member 250 will work as follows.Namely, when the clearance definition member 250 is housed in thecompartment 222, there are defined between the second support wall 252and the second side wall 227 of the engagement member 220 clearancessmaller than the depth of engagement between the engagement projection221 and threads 144 on the lead screw 140, for example, a depth of 0.1mm. Therefore, in the clearance definition member 250, the second sidewall 227 of the engagement member 220 is housed without forcing thesecond side wall 227 of the engagement member 220 toward the lead screw140. Also, since the clearance definition member 250 is rigid asmentioned above, even a misalignment between the engagement projection221 and threads 144, if any caused due to the dimensional tolerance ofthe engagement member 220 during movement of the pickup base 114, can belimited to within the clearance (0.1 mm) defined between the second sidewall 227 and second support wall 252 of the clearance definition member250. Thus, the engagement member 220 prevents the engagement projection221 from being misaligned to more than the depth of the threads 144 (0.3mm) and the lead screw 140 and engagement projection 221 from beingdisengaged from each other during movement of the pickup base 114.

Note that in case the second side wall having the engagement projection221 provided thereon is movable toward and away from the lead screw 140,the hinge 233 provided on the engagement member 220 may be anywhere onthe compartment 222 other than the base end of the second side wall 227.Also, the retaining projection 231 (232) to prevent the clearancedefinition member 223 (250) from being disengaged from the compartment222 may be provided on the clearance definition member 223 (250) andslits may be formed in the inner surfaces of the first and second sidewalls 226 and 227 to catch the clearance definition member.

As shown in FIG. 21, the base chassis 101 has connected thereto aprinted wiring board 161 having a drive circuit formed thereon. Theprinted wiring board 161 includes a so-called rigid circuit substratehaving a wiring pattern formed thereon and has mounted on the wiringpattern also various electronic parts such as a connector 162 forconnection of the FPC (flexible printed circuit) 23 mounted on theprinted wiring board 17 disposed on the lower half 9 of the device body7.

As shown in FIGS. 15 and 29, with the cover member 90 being fixed withbinding screws to the upper side of the base chassis 101 and the bottomplate 91 being fixed with binding screws at the lower side to the disktray 5, the above optical pickup unit 6 is held tight between the covermember 90 and bottom plate 91.

The cover member 90 has formed therein an opening 166 through which theobjective lens 108 and disk table 18 provided on the optical pickup unit103 are exposed upward. The opening 166 consists of an opening 166 aformed generally rectangular correspondingly to the moving range of thepickup base 114 to extend from the inner circumference to the outercircumference of the optical disk 4, and an opening 166 b formedgenerally circular correspondingly to the shape of the disk table 18 andcontiguously to the inner-circumferential end of the rectangular opening166 a. Also, the cover member 90 has formed thereon an abutting portion167 the top of the motor housing 145 for the feed motor 141 on thepickup base 114 formed on the base chassis 101 abuts.

With the cover member 90 being fixed with screws 135 to the upper sideof the base chassis 101, the disk table 18 and objective lens 108 on thepickup base 114 are directed upward through the opening 166. Also, whenthe motor housing 145 for the feed motor 141 abuts the rear side of theabutting portion 167, the cover member 90 closes the openings 142 in theupper side of the motor housing 145, to thereby close the magnetic fieldof the coil 146 housed in the motor housing 145.

When the base chassis 101 is housed in the compartment 21 for the disktray 5, the cover member 90 faces directly the optical disk 4 throughthe opening 16 in the disk tray 5 as shown in FIG. 36. Namely, the covermember 90 forms a part of the concavity 15. Since the cover member 90 isfixed with screws to the base chassis 101, it is closely attached to thebase chassis 101. Thus, it is blocked from lifting from the concavity15, and prevents the main surface of the cover member 90 and the end ofthe opening 166 from scratching the signal recording surface of theoptical disk 4.

The above cover member 90 is formed by punching an aluminum plate. Onthe lower side of the cover member 90, there is disposed the flexibleprinted wiring board 119 connected to the pickup base 114. On thisaccount, the cover member 90 is prepared by punching the aluminum platein a direction from the lower side toward the upper side with aconsideration against any burr which will possibly spoil the flexibleprinted wiring board 119. Thereafter, the cover member 90 is deburredalong the edge of the opening 166 and along the perimeter thereof.

The bottom plate 91 is also formed by punching an aluminum plate. Thebottom plate 91 has screw holes formed therein, and is fixed with screwsto the compartment 21 from the lower side of the base chassis 101 housedin the compartment 21 of the disk tray 5. Thus, the bottom plate 91itself is connected to the base chassis 101 with the base chassis 101being held tight between the bottom plate 91 and cover member 90.

The concavity 15 for housing the disk tray 5 the pickup base 114 anddisk table 18 are directed to face through the opening 166 in the covermember 90 is formed generally circular. As shown in FIG. 36, theconcavity 15 is defined by first to fourth walls 170 to 173 which areformed generally circular.

The first wall 170 is formed at the side of the front end 5 a of thedisk tray 5 to extend to over the opening 16 formed in the concavity 15.The first wall 170 has a constant clearance C defined between the loweredge of a wall body 170 a facing the concavity 15 and the cover member90 exposed through the opening 16 in the concavity 15. In this clearanceC, there is provided a projection 175 extending from the lower edge ofthe device body 7 toward the concavity 15.

The projection 175 is provided to prevent the cover member 90 exposedtrough the opening 16 from being deflected toward the signal recordingsurface of the optical disk 4. More specifically, the disk tray 5 isformed from rigid PPE (polyphenylene ether) containing glass in 20%, thebase chassis 101 of the optical pickup unit 6 housed in the disk tray 5is formed from iron (Fe), and the cover member 90 fixed to the upperside of the base chassis 101 and exposed through the opening 16 in thedisk tray 5 is formed from aluminum (Al). Namely, the disk tray 5, basechassis 101 and cover member 90 are formed from different materials,respectively, and thus different in coefficient of linear thermalexpansion from each other. The linear expansion coefficient of PPE isabout 2.8×10⁻⁵/mm° C., that of aluminum is about 2.4×10⁻⁵/mm° C., andthat of iron is about 1.2×10⁻⁵/mm° C.

Therefore, as the recorder/player 1 is put into operation and the disktray 5, base chassis 101 and cover member 90 have higher temperatures,these components will be distorted differently from each other due todifferences in linear expansion coefficient from each other. Morespecifically, the aluminum-made cover member 90 has the wall 166 a ofthe rectangular opening 166 deflected toward the optical disk 4. Thedeflected wall 166 a will possibly get into sliding touch with thesignal recording surface of the optical disk 4 received in the concavity15. The first wall 170 has the projection 175 formed on the lower edgeof the wall body 170 a and thus the cover member 90 abuts the projection175, which permits to prevent the cover member 90 from being deflectedtoward the optical disk 4.

Note that the screws 135 fixing the cover member 90 to the base chassis101 are made from a liquid crystal polymer lower in contractionpercentage. Therefore, the screws 135 limits the base chassis 101 andcover member 90 from being thermally distorted.

The second to fourth walls 171 to 173 are formed to rise from theconcavity 15 in a generally circular form.

Next, the FPC 23 which connects the disk tray 5 housing the opticalpickup unit 6 and the printed wiring board 17 provided on the lower half9 to each other will be described. As shown in FIG. 37, the FPC 23 isgenerally U-shaped and thus includes first and second arm portions 180and 181 both being linear, adjacent and parallel to each other, and ajoining portion 182 for connection of the first and second arm portions180 and 181 to each other.

The first arm portion 180 has formed at the free end thereof aconnection 183 for connection to a connector (not shown) provided on thebottom of the printed wiring board 17, and has attached on an endportion 180 a thereof a cover lay 184 to increase the rigidity of thearm portion 180. As shown in FIG. 38A, the first arm portion 180 has theend portion 180 a reinforced by the cover lay 184 directed toward therear wall 9 a of the lower half 9, and is connected to a connectorprovided on the bottom of the printed wiring board 17. Since the firstarm portion 180 has the end portion 180 a thereof improved in rigidityby the attached cover lay 184, the connection 183 can easily beconnected to the connector on the bottom of the printed wiring board 17.Also, the first arm portion 180 is fixed to the lower side of the lowerhalf 9.

The second arm portion 181 connected to the first arm portion 180 by theconnection 182 has formed at the end portion thereof a connection 186for connection to the connector 162 provided on the optical pickup unit6 housed in the disk tray 5. As shown in FIG. 38A, the second armportion 181 is folded back at the end portion 181 a toward the open endof the lower half 9 and extended toward the disk tray 5 and thus theconnection 186 is connected to the connector 162 of the optical pickupunit 6. Also, the second arm portion 181 is folded back at a point(indicated with a reference number 187) toward the open end of the lowerhalf 9.

Also, the second arm portion 181 has attached thereon in a positionsomewhat set back from the end portion 181 a toward the connection 182 acover lay 188 which enhances the rigidity of the second arm portion 181.That is, the second arm 181 is larger in rigidity in the portionsomewhat set back from the connection 186 toward the connection 182 thanthe portion including the connection 186. The cover lay 188 is attachedgenerally at the middle of the second arm portion 181 to increase therigidity of the portion of the second arm portion 181 having the coverlay 188 attached thereon in comparison with that of the other portionsincluding the connections 186 and 182.

The above second arm portion 181 is not fixed to the bottom of the lowerhalf 9 but is movable from the connection 182 into, and to outside, thedevice body 7 as the disk tray 5 is moved, as shown in FIGS. 38A and38B. Also, the bending 187 of the second arm portion 181 shifts in themoving direction of the disk tray 5 as the latter is moved, as shown inFIGS. 39A to 39C.

Note here that the length of the portion, not fixed to the bottom of thelower half 9 and formed flexibly deformable, of the second arm portion181 is generally a half of the moving distance of the disk tray 5 andthe boundary thereof with respect to the connection 182 is generally atthe middle of the moving range of the disk tray 5. In other words, thesecond arm portion 181 has a necessary minimum length for the movementof the disk tray 5 or a little larger length. As the disk tray 5 ismoved, the second arm portion 181 is moved to outside the lower half 9from the boundary thereof with respect to the connection 182 fixed tothe bottom of the lower half 9, and thus bent at a base end portion 181b thereof and then drawn out of the device body 7. Also, when the secondarm portion 181 is moved into the lower half 9, it is housed into thedevice body 7 with bending of the end portion 181 a thereof having theconnection 186 formed thereon.

More specifically, when the disk tray 5 is ejected to outside the devicebody 7, the second arm portion 181 has the end portion 181 a thereofejected to outside the device body 7 and the bending 187 is formed nearthe connection 182, as shown in FIG. 39A. Next, as the disk tray 5 ismoved into the device body 7 and also the second arm portion 181 is alsomoved into the device body 7, the bending 187 shifts toward the endportion 181 a as shown in FIG. 39B. Then, when the disk tray 5 is fullyhoused into the device body 7, the second arm portion 181 will have thebending 187 formed near the connection 186 as shown in FIG. 39C.

As mentioned above, in the second arm portion 181, the portion thereofnear the connection 186 is relatively lower in rigidity than the portionthereof somewhat set back toward the connection 182 and on which thecover lay 188 is attached. Thus, even when the bending 187 of the secondarm portion 181 is formed near the connection 186 with the disk tray 5being housed in the device body 7 as shown in FIGS. 28B and 39C, theload applied to the second arm portion 181 due to the bending can bereduced. Thus, the second arm portion 181 can prevent the circuitpattern formed on the FPC 23 from being broken due to a cracking takingplace in the end portion 181 a.

Also, since the second arm portion 181 reduces the load applied theretodue to the bending 187 formed near the connection 186, it is notnecessary to increase the distance between the connection 186 andbending 187 at the time of housing the disk tray 5 into the device body7 in order to reduce the load applied to the second arm portion 181 dueto the bending. Thus, the second arm portion 181 may not have any extralength, which will advantageously lead to a reduction of the cost ofmanufacture.

Further, the device body 7 of the recorder/player 1 has to be limited inthickness because many available host apparatuses are designed thinner.When the height of the space where the FPC 23 is disposed has to belimited, the bending 187 should be made to have a larger curvature andthus the load to the bending 187 will be larger. However, since thesecond arm portion 181 can reduce the load to the bending 187 when thedisk tray 5 is housed into the device body 7, the present invention canmeet the requirement for a thinner design of the device body 7.

Note that the FPC 23 has the cover lay 188 attached generally on themiddle of the second arm portion 181 thereof so that it will not becaught between the device body 7 and the rear end 5 d of the disk tray 5when the disk tray 5 is housed into the device body 7. Morespecifically, when the disk tray 5 is outside the device body 7, aclearance 190 is defined between the disk tray 6 and device body 7 asshown in FIG. 39A. Therefore, when the flexible second arm portion 181is deflected generally at the intermediate portion thereof to below theclearance 190 downward at the time of housing the disk tray 5 into thedevice body 7, it will be caught nearly at the middle thereof betweenthe rear end 5 d of the disk tray 5 and the device body 7.

Note here that in the FPC 23, the cover lay 188 provided generally atthe middle of the second arm portion 181 makes the rigidity generally atthe middle of the second arm portion 181 higher than that of the rearend portion 181 b. Therefore, when the disk tray 5 once ejected tooutside the device body 7 is housed back into the device body 7, themiddle of the second arm portion 181, higher in rigidity, is preventedfrom being deflected to below the clearance 190 while the rear endportion 181 b of the second arm portion 181, lower in rigidity and moreflexible, is bent, to assure a positive movement of the disk tray 5 intothe device body 7.

Next, the recorder/player 1 constructed as having been described abovewill be described concerning its circuit configuration.

The recorder/player 1 according to the present invention writes data tothe optical disk 4 by projecting a light beam to the optical disk 4, andreads data recorded in the optical disk 4 by detecting a return lightfrom the optical disk 4. As shown in FIG. 40, the recorder/player 1includes a spindle motor 201 to rotate the optical disk 4, a motorcontrol circuit 202 to control the spindle motor 201, the optical pickup103 to detect a return light from the optical disk by projecting a lightbeam to the optical disk 4 being rotated by the spindle motor 201, an RFamplifier 203 to amplify an electrical signal output from the opticalpickup 103, a servo circuit 204 to generate a focusing servo signal andtracking servo signal for the objective lens 108, and a subcodeextraction circuit 205 to extract a subcode. Also, the recorder/player 1additionally includes a recording system including an input terminal 206connected to the host apparatus 2 such as a personal computer or thelike to receive recording data, an error correction/encoding circuit 207which makes error correction and encodes recording data supplied at theinput terminal 206, a modulation circuit 208 to modulate theerror-corrected and encoded data from the circuit 207, and a recordingcircuit 209 to record the modulated recording data. In addition, therecorder/player 1 includes a playback system including a demodulationcircuit 210 to demodulate read data from the optical disk 4, an errorcorrection/decoding circuit 211 to make error correction/decoding of thedemodulated read data, and an output terminal 212 to provide theerror-corrected and decoded data. The recorder/player 1 further includesa user's control unit 213 to make input of a command signal for thedevice, a memory 214 to store various control data etc., and a controlcircuit 215 to control the system operation.

The above spindle motor 201 has provided on the spindle thereof the disktable 102 on which an optical disk 4 is to be placed, and it rotates theoptical disk on the disk table 102. The motor control circuit 202controls the spindle motor 201 to rotate the optical disk 4 at a CLV(constant linear velocity). More particularly, the motor control circuit202 controls the spindle motor 201 for the optical disk 4 to be rotatedat CLV on the basis of a reference clock from a crystal oscillator and aclock from a PLL circuit. Of course, the optical disk 4 may be rotatedat a CAV (constant angular velocity) or at a combination of CLV and CAV.

The above optical pickup 103 includes a semiconductor laser which canemit a light beam having a wavelength corresponding to the type of theoptical disk 4 set in the recorder/player 1, objective lens 108 having anumerical aperture corresponding to the type of the optical disk 4 andwhich focuses the light beam emitted from the semiconductor laser,photodetector to detect a return light from the optical disk 4, etc.When reading data recorded in the optical disk 4, the optical pickup 103sets the output of the semiconductor laser to a standard level andcontrols the semiconductor laser to emit a laser light. Also, whenwriting recording data to the optical disk 4, the optical pickup 103sets the semiconductor laser output to a recording level higher than thestandard level for the data reading and controls the semiconductor laserto emit a laser light. For both data write and read, the optical pickup103 projects the light beam to the optical disk 4, detects a returnlight from the signal recording surface of the optical disk 4 by thephotodetector, and makes photoelectric conversion of the detected light.Also, the objective lens 108 is held by an objective lens drivemechanism such as a biaxial actuator or the like, and moved by the drivemechanism in a focusing direction parallel to the optical axis thereofon the basis of a focusing servo signal and in a tracking directionperpendicular to the optical axis thereof on the basis of a trackingservo signal.

The above RF amplifier 203 generates an RF signal, and focusing andtracking error signals on the basis of the electric signal output fromthe photodetector included in the optical pickup 103. For example, thefocusing error signal is generated by the astigmatism method, and atracking error signal is generated by the three-beam method or push-pullmethod. When in the playback mode, the RF amplifier 203 provides the RFsignal to the demodulation circuit 210 while providing the focusing andtracking error signals to the servo circuit 204.

The above servo circuit 204 generates a servo signal for playback of theoptical disk 4. More specifically, the servo circuit 204 generates,based on a focusing error signal supplied from the RF amplifier 203, afocusing servo signal with which the focusing error signal becomes zero,and based on a tracking error signal supplied from the RF amplifier 203,a tracking servo signal with which the tracking error signal becomeszero. Then, the servo circuit 204 provides the focusing and trackingservo signals to a drive circuit in the objective lens drive mechanismincluded in the optical pickup 103. The drive circuit drives the biaxialactuator on the basis of the focusing servo signal to move the objectivelens 108 in a focusing direction parallel to the optical axis of theobjective lens 108, and on the basis of the tracking servo signal tomove the objective lens 108 in a tracking direction perpendicular to theoptical axis of the objective lens 108.

The above subcode extraction circuit 205 extracts subcode data from theRF signal output from the RF amplifier 203 and provides the extractedsubcode data to the control circuit 215 which will thus be able toidentify address data etc.

An input terminal 206 is electrically connected to an interface such asSCSI (small computer system interface), ATAPI (advanced technologyattachment packet interface), USB (universal serial bus), IEEE(Institute of Electrical and Electronic Engineers) 1394 or the like ofthe host apparatus 2 such as a personal computer or the like to receiverecording data for audio data, movie data, computer program,computer-processed data or the like from the host apparatus 2 andprovide the supplied recording data to the error correction/encodingcircuit 207.

The above error correction/encoding circuit 207 makes an errorcorrection/encoding such as CIRC (cross interleave Reed-Solomon coding)or Reed-Solomon Product Coding and provides the error-corrected andencoded recording data to the modulation circuit 208. Havingeight-to-ten and eight-to-sixteen conversion tables, the modulationcircuit 208 converts the supplied 8-bit recording data into 14- or16-bit data, and provides the data to a recording circuit 209. Therecording circuit 209 makes a recording compensation such as NRZ(non-return to zero), NRZI (non-return to zero inverted) or the like andprovides the processed data to the optical pickup 103.

The demodulation circuit 210 has similar conversion tables to those inthe modulation circuit 208 to convert an RF signal supplied from the RFamplifier 203 from 14 or 16 bits to 8 bits, and provides the converted8-bit read data to the error connection/decoding circuit 211. The errorcorrection/decoding circuit 211 makes a error correction and decoding ofdata supplied from the demodulation circuit 210, and provides the datato the output terminal 212. The output terminal 212 is electricallyconnected to the aforementioned interface of the host apparatus 2. Theread data provided from the output terminal 212 is displayed on amonitor connected to the host apparatus 2 and converted by a speakerinto an audible sound.

The user's control unit 213 generates various command signals foroperation of the recorder/player 1, and provides the signals thusgenerated to the control circuit 215. More particularly, the user'scontrol unit 213 is provided with an eject button 213 a, and inaddition, with a record button 213 b to start write of recording data toan optical disk 4 set in place on the disk table 102, a play button 213c to start read of data recorded in the optical disk 4, and a stopbutton 213 d to stop the record and playback operations. For example,when the user operates a keyboard, mouse or the like of the hostapparatus 2, the eject button 213 a, record button 213 b, play button213 c and stop button 213 d provide record start signal, playback startsignal, stop signal, etc. to the control circuit 215 from the hostapparatus 2 via the interface.

The above memory 214 is a EP-ROM (erasable programmable read-onlymemory) or the like, for example, to store various control data andprograms used in the control circuit 215. More specifically, data storedin the memory 214 include various control data for the feed motor 141(step motor) to move the optical pickup 103 radially of an optical disk4 set in place on the disk table 102.

Note here that the optical disk 4 has a lead-in area formed in aninner-circumferential area thereof, a program area formed in an areaoutside the lead-in area, and a lead-out area formed outside the programarea, that is, in the outermost-circumferential area thereof. In thesubcode data in the lead-in area, there are stored TOC (table ofcontents) data such as address data on data stored in the program areaand address data on data stored in the lead-out area. Also, the feedmotor 141 is supplied with a pulsed voltage to feed the optical pickup103 stepwise. On this account, the memory 214 stores a number of writeand read steps (A) required for moving the optical pickup 103 in a rangefrom a beginning (HOME) of the lead-in area to an end (OUT) of theoutermost lead-out area, in which range the optical pickup 103 can readdata from the optical disk 4, as shown in FIG. 41. It should be notedthat when the optical pickup 103 has arrived at the end position (OUT),it will mechanically be limited from moving and cannot move further tothe outer circumference of the optical disk 4.

Also, the movable range of the optical pickup 103 can be shifted to aposition inner than the lead-in area in the optical disk 4 so that theoptical pickup 103 can positively read TOC data in the lead-in area. Onthis account, the memory 214 further stores a number of steps (B)required for movement of the optical pickup 103 from aninnermost-circumferential position (IN) of the optical pickup 103 to thebeginning (HOME) of the lead-in area. When the optical pickup 103 hasarrived at its IN position, it will mechanically be limited from movingand cannot move further inwardly.

The movable range of the optical pickup 103 extends from theinnermost-circumferential position (IN) to the end (OUT) of the lead-outarea, in which range the optical pickup 103 can read data from theoptical disk 4, and thus the optical pickup 103 has to accurately bepositioned in a mechanical manner. On this account, the memory 214stores a maximum number of steps (C) for the step motor or feed motor141. The maximum number of steps (C) includes a number of extra steps(D) applied to an area inner than the innermost-circumferential position(IN) for a positive arrival of the optical pickup 103 at theinnermost-circumferential position (IN), and also applied to an areaouter than the end position (OUT) for a positive arrival of the opticalpickup 103 at the end position (OUT). In the areas to which the numberof extra steps (D) is applied, the optical pickup 103 is mechanicallylimited from moving, that is, immovable. In this immovable condition,the step motor 141 is supplied with an additional pulse voltage torotate the lead screw. This idle rotation of the lead screw will cause anoise.

As shown in FIG. 40, the control circuit 215 includes a microcomputer,CPU (central processing unit), etc. to control the system operation inresponse to command signals supplied from the user's control unit 213.As shown in FIG. 41, the control circuit 215 counts the positions of theoptical pickup 103 taking the beginning (HOME) of the lead-in area as“0”. Also, with the optical disk 4 is ejected, the control circuit 215supplies a power to the on-core coil 44 to cancel the magnetic force ofthe magnet attracting the plunger 45 magnetically and thus disengagingthe engagement mechanism 20 of the disk tray 5 from the engagementconcavity 11 of the device body 7.

The recorder/player 1 constructed as above functions as will bedescribed below:

In the recorder/player 1, the skew adjusting mechanism 109 pre-supportsthe pair of guide shafts 105 and 106 at the opposite ends of the latter.The skew adjusting mechanism 109 adjusts the inclination of the guideshafts 105 and 106 so that the light beam projected from the objectivelens 108 will be incident perpendicularly upon the signal recordingsurface of the optical disk. The elastic member 126 disposed inside thehousing 125 for the skew adjusting mechanism 109 is hardened with theadhesive 133. Thus, even if the elastic member 126 is plasticallydeformed due to compression by the adjusting screw 127, the skewadjusting mechanism 109 can maintain an appropriate inclination of theguide shafts 105 and 106.

In the recorder/player 1, the disk tray 5 is ejected to outside thedevice body 7 for setting an optical disk 4 onto the disk tray 5. Atthis time, the pivoting piece 42 is forced in the direction of arrow Eand thus the device body 7 is in touch with the stop wall 81 provided onthe disk tray 5 as shown in FIG. 19. Also, the engagement piece 41 hasthe abutting portion 51 thereof pivoted by the pivoting-range limitingprojection 55 of the pivoting piece 42 in the direction opposite to thedirection of arrow D and thus the engagement portion 48 thereof heldretracted from the moving orbit of the engagement projection 11.Therefore, the lower half 9 of the device body 7 on which the engagementprojection 11 is provided upright and the disk tray 5 are disengagedfrom each other, and the ejection member 30 forced by the coil spring 28provided on the disk tray 5 forces the rear wall 9 a of the lower half 9and thus the disk tray 5 is ejected out of the device body 7.

When an optical disk 4 is set in place in the concavity 15 of the disktray 5 and the disk tray 5 is introduced by the user into the devicebody 7, the engagement projection 11 provided upright on the lower half9 moves forward in the direction of arrow H in FIG. 19 until it gets intouch with the arm portion 70 of the pressing piece 46, and the armportion 70 is thus pivoted in the direction of arrow G in FIG. 20. Asthe arm portion 70 is thus pivoted, the pressing portion 72 of thepressing piece 46 presses the contact portion 57 of the pivoting piece42 to pivot the pivoting piece in the direction opposite to thedirection of arrow E in FIG. 20. The plunger 45 connected to theconnection 58 of the pivoting piece 42 has the insertion shaft 63thereof inserted deep into the on-core coil 44 and magneticallyattracted by the magnet disposed in the on-core coil 44.

Since the contact portion 57 put into contact with the pressing portion72 of the pressing piece 46 has the protrusion 60 formed thereon, thepressing piece 46 can press the protrusion 60 to positively pivot thepivoting piece 42 in the direction opposite to the direction of E andthus permit the plunger 45 to be attracted by the magnet built in theon-core coil 44. Also, since the slit 61 is formed between the contactportion 57 and connection 58 and the contact portion 57 is elasticallydisplaceable, the pivoting piece 42 can have the contact portion 57deflect even when it is excessively pressed by the pressing piece 46,thus permitting to absorb the pressure.

Thus, the plunger 45 and pivoting piece 42 are held pivoted in thedirection opposite to the direction of arrow E in FIG. 20 against theforce of the torsion coil spring 59. As the pivoting-range limitingprojection 55 of the pivoting piece 42 is pivoted in the directionopposite to the direction of arrow E, the engagement piece 41 is allowedto pivot in an increased range in the direction of arrow D and hence theengagement portion 48 is positioned on the moving orbit of theengagement projection 11 as shown in FIG. 20.

As the disk tray 5 is inserted deeper into the device body 7, theengagement projection 11 moves in the direction of arrow H in FIG. 20while pivoting the bevel 49 a formed on the end portion of the body 49of the engagement piece 41 in the direction opposite to the direction ofarrow D, and is engaged on the engagement portion 48. Thus, the disktray 5 and the lower half 9 of the device body 7 are engaged on eachother.

As shown in FIG. 18, the ejection member 30 is pressed back from therear wall 9 a of the lower half 9 and moves toward the front end 5 awhile compressing the coil spring 28 by the flange 30 a toward the frontend 5 a. Since the end portion at the side of the front end 5 a isretained by the compartment wall 29 a of the spring compartment 29, thecoil spring 28 is pressed and thus compressed by the flange 30 a tomaintain the force for forcing the flange 30 a toward the rear end 5 d.That is, the disk tray 5 engages the engagement projection 11 providedupright on the lower half 9 onto the engagement piece 41 while forcingthe lower half 9 toward the rear end 5 d, and it is thus held inside thedevice body 7.

Also, when the disk tray 5 is housed into the device body 7, the FPC 23connecting the optical pickup unit 6 housed in the disk tray 5 and theprinted wiring board 17 disposed on the lower half 9 of the device body7 is deflected at the end portion 181 a of the second arm portion 181and the bending 187 formed at the rear end portion 181 b shifts into thedevice body 7 while moving toward the end portion 181 a. Since the FPC23 has the cover lay 188 attached generally at the middle of the secondarm portion 181, the second arm portion 181 is more rigid generally atthe middle thereof than the rear end portion 181 b. Therefore, when thedisk tray 5 once ejected to outside the device body 7 is housed againinto the device body 7, the second arm portion 181 is prevented frombeing deflected at the higher-rigidity middle portion thereof to belowthe clearance 190, while the rear end portion 181 b of the second armportion 181, lower in rigidity and more flexible, is bent and positivelymoved into the device body 7.

Also, when the disk tray 5 is fully housed in the device body 7, thesecond arm portion 181 is bent (indicated with the reference number 187)near the connection 186 with the connector 162 as shown in FIGS. 38B and39C. However, since the rigidity of the portion, near the connection186, of the second arm portion 181 is lower than that of the portionsomewhat set back toward the connection 182 where the cover lay 188 isattached, it is possible to reduce the load applied to the second armportion 181 due to the bending. Therefore, the second arm portion 181can prevent the end portion 181 a thereof from being cracked to breakthe circuit pattern formed in the FPC 23.

Also, since the second arm portion 181 reduces the load applied theretodue to the bending 187 formed near the connection 186, it is notnecessary to increase the distance between the connection 186 andbending 187 at the time of housing the disk tray 5 into the device body7 in order to reduce the load applied to the second arm portion 181 dueto the bending. Thus, the second arm portion 181 may not have any extralength, which will advantageously lead to a reduction of the cost ofmanufacture.

Further, in the thin-designed recorder/player 1, since the height of thespace where the FPC 23 is limited to the maximum possible extent forhousing the disk tray 5, the bending 187 should be made to have a largercurvature and thus the load to the bending 187 will be larger. However,since the second arm portion 181 can reduce the load to the bending 187when the disk tray 5 is housed into the device body 7, the presentinvention can meet the requirement for a thinner design of the devicebody 7.

Also, in the recorder/player 1, the optical pickup 103 is normallypositioned at the beginning (HOME) of the lead-in area. Since therecorder/player 1 is to be incorporated in a portable apparatus such asnotebook computer or the like, it may possibly be applied with avibration when the portable apparatus is being carried or in a similarcondition. When the host apparatus 2 having the recorder/player 1 builttherein is being carried with an optical disk 4 being set on the disktray 5, it is likely that a vibration, if any applied to the hostapparatus 2, will cause the optical disk 4 to be rattled. Thedisplacement of the optical disk 4, due to the rattling, is larger atthe outer circumference. On this account, the recorder/player 1 isdesigned according to the present invention such that the optical pickup103 is positioned at the inner circumference of the optical disk 4 wherethe rattling-caused displacement is small, to thereby prevent theoptical disk 4 and the objective lens 108 of the optical pickup 103 orthe like from getting into touch with each other to scratch each other.

As shown in FIG. 42, after the recorder/player 1 is switched on in stepS1, the control circuit 215 drives the step motor 141 in step S2. Morespecifically, the control circuit 215 applies a pulsed voltageequivalent to the maximum number of steps (C) to the step motor 141.Then, the lead screw 140 connected to the step motor 141 is rotated andthe optical pickup 103 is moved stepwise to the end position (OUT) atthe outer circumference of the optical disk 4.

In the recorder/player 1, if a vibration is applied thereto while it isbeing carried, the optical pickup 103 may possibly move, by jumping,from the beginning (HOME) of the lead-in area toward the inner or outercircumference of the optical disk 4. Even is such an event, the stepmotor 141 is applied with a pulsed voltage equivalent to the maximumnumber of steps (C) resulted from addition, to the number of write andread steps (A) in FIG. 41, of the number of steps (B) required formovement of the optical pickup 103 from its innermost-circumferentialposition (IN) to the beginning (HOME) of the lead-in area and the numberof extra steps (D) at the inner and outer circumferences. That is, sincethe step motor 141 is driven until the lead screw 140 rotates idly afterthe optical pickup 103 is mechanically limited from moving beyond theend position (OUT), the end position (OUT) of the optical pickup 103 canpositively be indexed.

Note that when the lead screw 140 is rotating idly, it will cause anoise. However, the noise occurs only for a period corresponding to thesum of the number of steps (B) required for movement of the opticalpickup 103 from its innermost-circumferential position (IN) to thebeginning (HOME) of the lead-in area and the number of extra steps atthe inner and outer circumferences and the number of extra steps (D).Therefore, the noise can be suppressed to be smaller than that when thestep motor 141 is applied with a negative pulsed voltage equivalent tothe maximum number of steps (C) in a direction from the beginning (HOME)of the lead-in area toward the innermost-circumferential position (IN),for example.

When the end position (OUT) of the optical pickup 103 is positivelyidentified in step S2, the control circuit 215 applies, in step S3, thestep motor 141 with a negative pulsed voltage equivalent to the maximumnumber of steps (C). Thus, after the optical pickup 103 is mechanicallylimited from moving being the innermost-circumferential position (IN),the step motor 141 is driven until the lead screw 140 rotates idly,whereby the innermost-circumferential position (IN) of the opticalpickup 103 can positively be indexed.

Note that when the lead screw 140 is rotating idly, it will cause anoise. However, the noise occurs only for a period corresponding to thenumber of extra steps (D) at the inner circumference and the time ofnoise occurrence is caused can be minimized.

When the innermost-circumference position (IN) of the optical pickup 103is positively identified in step S3, the control circuit 215 applies, instep S4, the step motor 141 with a negative pulsed voltage equivalent tothe number of steps (B) required for movement of the optical pickup 103from the innermost-circumferential position (IN) of the optical pickup103 to the beginning (HOME) of the lead-in area. Thus, the controlcircuit 215 can positively move the optical pickup 103 to the beginning(HOME) of the lead-in area. Also, the control circuit 215 sets thebeginning (HOME) of the lead-in area to zero, starts counting the pulsesand starts managing the position of the optical pickup 103.

The recorder/player 1 operates for writing recording data to the opticaldisk 4 as will be described below:

When the user pushes the record button 213 a on the user's control unit213, recording data is supplied at the input terminal 206 of therecorder/player 1. The recording data undergoes, in the errorcorrection/encoding circuit 207, an error correction and encodingcorresponding to the type of an optical disk 4 currently used in therecorder/player 1, and next in the modulation circuit 208, a modulationcorresponding to the type of the optical disk 4. The modulated data isrecorded in the recording circuit 209, and then supplied to the opticalpickup 103. Then, the optical pickup 103 projects, to the recordinglayer of the optical disk 4, a light beam emitted from the semiconductorlaser and having a wavelength corresponding to the type of the opticaldisk 4, detects a return light from the reflection layer in the opticaldisk 4, makes a photoelectric conversion of the detected light, andprovides the resultant electrical signal to the RF amplifier 203. The RFamplifier 203 will generate a focusing error signal, tracking errorsignal and an RF signal. The servo circuit 204 generates a focusingservo signal and tracking servo signal on the basis of the focusingerror signal and tracking error signal supplied from the RF amplifier203, and provides the servo signals to the drive circuit in theobjective lens drive mechanism included in the optical pickup 103. Thus,the objective lens 108 held by the objective lens drive mechanism ismoved in a focusing direction parallel to the optical axis of theobjective lens 108 and in a tracking direction perpendicular to theoptical axis of the objective lens 108. Further, the motor controlcircuit 202 generates a rotation servo signal with which a clockgenerated from a wobble component of a groove and an addressing pit willbe synchronous with a reference clock from the crystal oscillator, anddrives the spindle motor 201 on the basis of the rotation servo signalto rotate the optical disk 4 at CLV. Furthermore, the subcode extractioncircuit 205 extracts a wobbled groove from the RF signal and addressdata on the lead-in area from the pit pattern, and provides theextracted data to the control circuit 215. To write data processed inthe recording circuit 209 under the control of the control circuit 215,the optical pickup 103 accesses a predetermined address on the basis ofthe extracted address data, drives the semiconductor laser at therecording level, and projects the light beam to the recording layer ofthe optical disk 4 to write the data to the optical disk 4. As theoptical pickup 103 writes the recording data, it is moved stepwise bythe step motor 141 to write the recording data over the area between theinner and outer circumferences of the optical disk 4.

The recorder/player 1 operates for reading data recorded in the opticaldisk 4 as will be described below:

When the user pushes the play button 213 c on the user's control unit213, the optical pickup 103 will project, to the recording layer of theoptical disk 4, a light beam emitted from the semiconductor laser andhaving a wavelength corresponding to the type of the optical disk 4,detects a return light from the reflection layer in the optical disk 4,makes a photoelectric conversion of the detected light, and provides theresultant electrical signal to the RF amplifier 203. The RF amplifier203 will generate a focusing error signal, tracking error signal and anRF signal. The servo circuit 204 generates a focusing servo signal andtracking servo signal on the basis of the focusing error signal andtracking error signal supplied from the RF amplifier 203, and controlsthe focus and tracking of the objective lens 108 on the basis of theseservo signals. Further, the motor control circuit 202 generates arotation servo signal with which a clock generated from a sync signalwill be synchronous with the reference clock from the crystaloscillator, and drives the spindle motor 201 on the basis of therotation servo signal to rotate the optical disk 4 at CLV. Furthermore,the subcode extraction circuit 205 extracts subcode data from the RFsignal, and provides the extracted subcode data to the control circuit215. To read data, the optical pickup 103 accesses a predeterminedaddress on the basis of address data included in the extracted subcodedata, drives the semiconductor laser at the playback level, and projectsthe light beam to the recording layer of the optical disk 4 to readrecorded in the optical disk 4. As the optical pickup 103 reads the datafrom the optical disk 4, it is moved stepwise by the step motor 141 toread the data over the area between the inner and outer circumferencesof the optical disk 4.

The RF signal generated by the RF amplifier 203 is demodulated in thedemodulation circuit 210 correspondingly to a method used for modulationof the data for recording, undergoes and the error correction/decodingin the error correction/decoding circuit 211, and then is delivered atthe output terminal 212. Thereafter, the data delivered at the outputterminal 212 is outputted as it is in the digital form or converted by aD-A (digital-to-analog) converter from digital to analog, for example,and supplied to the speaker, monitor or the like.

When writing or reading data to or from the optical disk 4 as above, theengagement projection 151, formed in the compartment 153, of theengagement member 120 connected to the pickup base 114 having theobjective lens 108 provided thereon in the threads 144 on the lead screw140 to the depth of the threads 144, for example, to a depth of 0.3 mm,and the clearance definition member 152 formed from a rigid metallicplate inside the compartment 153 is housed between the support walls 158and 159 of the compartment 153 with a space, between them, smaller thanthe depth of engagement between the engagement projection 151 andthreads 144 on the lead screw 140, for example, with a clearance of 0.1mm.

Therefore, the clearance definition member 152 is housed without forcingthe engagement projection 151 formed on the side wall 153 a to the leadscrew 140. That is, it is possible to prevent the lead screw 140 frombeing applied with any excessive force and thus the rotation of the leadscrew 140 from being dulled. Thus it is assured that the lead screw 140can be rotated smoothly. Also, the clearance definition member 152 canlimit any misalignment of the engagement projection 151 in relation tothe threads 144, caused by the dimensional tolerance of the engagementmember 120 during movement of the pickup base 114, to smaller than aclearance (0.1 mm) defined between the side wall 153 a of thecompartment 153 and support wall 158 of the clearance definition member152. Thus, the engagement member 120 can limit the misalignment of theengagement projection 151 to less than the depth (0.3 mm) of the threads144 to prevent the lead screw 140 and engagement projection 151 fromdisengaged from each other during movement of the pickup base 114.

Also, the engagement member 120 in which the clearance definition member220 (250) is housed works effectively as follows. Even if therecorder/player 1 is dropped by mistake and the pickup base 114 quicklyslides on the guide shafts 105 and 106 and thus the engagement member220 installed on the pickup base 114 quickly slides on the lead screw140, both the edges 227 a and 227 b of the second side wall 227 havingformed thereon the engagement projection 221 which is in mesh with thethreads 144 on the lead screw 140 are supported by the support piece 240(253) of the clearance definition member 220 (250) or at the folds 254.Therefore, it is possible to relieve the load concentrated to the hinge233 supporting the second side wall 227 and thus prevent the hinge 223from being broken.

Also, the feed motor 141, which is supplied with a rectangular wave tofeed the pickup base 114 as the lead screw 140 is rotated, is designedthinner because the motor housing 145 is open at the top and bottomthereof. Further, the motor housing 145 is held between the cover member90 and bottom plate 91 disposed on the top and bottom, respectively, ofthe optical pickup unit 6.

As above, the magnetic field of the coil 146 housed in the motor housing145 can be closed, so that the fringe magnetic field from the feed motor1 can be inhibited from adversely affecting write or read of informationsignals to or from the optical disk 4. Also, since the motor housing 145for the feed motor 141 is open at both the top and bottom thereof, theheat can easily be discharged from inside the motor housing 145.

Also, in the recorder/player 1, the disk tray 5, base chassis 101 andcover member 90 are made of materials different in coefficient of linearthermal expansion from each other, respectively, these components willbe distorted differently from each other due to the differences inlinear expansion coefficient from each other when have highertemperatures, these components. More specifically, the aluminum-madecover member 90 has the wall 166 a of the rectangular opening 166deflected toward the optical disk 4, and the deflected wall 166 a willpossibly get into sliding touch with the signal recording surface of theoptical disk 4 received in the concavity 15.

The first wall 170 has the projection 175 formed on the lower edge ofthe wall body 170 a and thus the cover member 90 abuts the projection175, which permits to prevent the cover member 90 from being deflectedtoward the optical disk 4 and thus prevent the cover member 90 fromgetting into sliding contact with the optical disk 4.

The recorder/player 1 operates when the eject button 213 a for ejectionof the optical disk 4 is pressed, as will be described below withreference to FIG. 43:

In step S11, the control circuit 215 judges whether the eject button 213a has been pressed by the user. When the result of judgment isaffirmative, the control circuit 215 goes to step S12. When the controlcircuit 215 has detected that the user has pressed the eject button 213a, it will apply the step motor 141 with a negative pulsed voltage tomove the optical pickup 103 to the beginning (HOME) of the lead-in area.

Note that for movement of the optical pickup 103 to the beginning (HOME)of the lead-in area, a negative pulsed voltage equivalent to the maximumnumber of steps (C) may be applied to the step motor 141 to move theoptical pickup 103 to its innermost-circumferential position (IN) andthen a positive pulsed voltage, equivalent to the number of steps (B)required for movement of the optical pickup 103 from theinnermost-circumferential position (IN) of the optical pickup 103 to thebeginning (HOME) of the lead-in area, be applied to the step motor 141to move the optical pickup 103 to the beginning (HOME) of the lead-inarea.

When the optical pickup 103 has arrived at the beginning (HOME) of thelead-in area, the control circuit 215 goes to step S13 where it willsupply the on-core coil 44 with to cancel the magnetic force of themagnet which magnetically attracts the plunger 45 in order to disengagethe engagement mechanism for the disk tray 5 and engagement projection11 of the device body 7 from each other. Thus, the disk tray 5 havingthe optical disk 4 placed thereon is ejected to outside the device body7 under the force of the coil spring 28.

More specifically, to eject the disk tray 5 from inside the device body7, the control circuit 215 having received a command signal from theuser's control unit 213 provided on the disk tray 5 supplies a currentto cancel the magnetic force of the magnet built in the on-core coil 44.Therefore, the pivoting piece 42 is pivoted under the force of thetorsion coil spring 59 in the direction of arrow E in FIG. 19. Thepivoting-range limiting projection 55 is pivoted in the direction ofarrow E and thus the engagement piece 41 is pivoted in the directionopposite to the direction of arrow D, so that the engagement portion 48will be retracted from one the moving orbit of the engagement projection11. Thus, the engagement projection 11 is disconnected from theengagement portion 48, and thus the disk tray 5 is disengaged from thelower half 9 of the device body 7.

At this time, the ejection member 30 is applied with a reaction equal tothe force of the coil spring 28 from the rear wall 9 a to press the coilspring 28 back to the front end 5 a by the flange 30 a. Since the endthereof at the side of the front end 5 a is retained by the wall 29 a ofthe coil compartment 29, the coil spring 28 will expand while forcingthe compartment wall 29 a out toward the front end 5 a. Thus, the disktray 5 is forced out toward the open end of the device body 7 and theside thereof at the side of the front end 5 a is ejected toward the openend of the device body 7.

Note that since the arm portion 70 is retained by the stopper 80 alsowhen pivoting of the pivoting piece 42 in the direction of arrow E hascaused the pressing portion 72 of the pressing piece 46 to collide withthe contact portion 57 of the pivoting piece 42 and thus pivoted thepressing portion 72 in the direction opposite to the direction of arrowG, it can be avoided that the arm portion 70 will excessively be pivotedand not be positioned on the moving orbit of the engagement projection11. Also, the torsion coil spring 73 wound on the pressing piece 46 canbe retained in an appropriate position by the retaining member 75 formedon the rear side 5 c of the disk tray 5 and thus provides an optimumforce to the pressing piece 46. Therefore, even when having been pressedby the engagement projection 11 and pivoting piece 42 and pivoted in thedirection of arrow G or in the direction opposite to the direction ofarrow G, the pressing piece 46 is returned to the initial position wherethe arm portion 70 intersects the moving orbit of the engagementprojection 11.

Note here that when the optical disk 4 is ejected, a vibration willpossibly cause it to rattle. The displacement of the optical disk 4, dueto the rattling, is larger at the outer circumference. On this account,the recorder/player 1 is designed according to the present inventionsuch that the optical pickup 103 is positioned at the innercircumference of the optical disk 4 where the rattling-causeddisplacement is small, to thereby prevent the optical disk 4 and theobjective lens 108 of the optical pickup 103 or the like from gettinginto touch with each other to scratch each other.

In the foregoing, the present invention has been described in detailconcerning certain preferred embodiments thereof as examples withreference to the accompanying drawings. However, it should be understoodby those ordinarily skilled in the art that the present invention is notlimited to the embodiments but can be modified in various manners,constructed alternatively or embodied in various other forms withoutdeparting from the scope and spirit thereof as set forth and defined inthe appended claims. For example, the present invention is alsoapplicable to a recorder/player designed for use with an optical disksuch as CD (compact disk), CD-ROM, CD-R/RW, DVD-ROM or DVD-RAM.

Also, the host apparatus in which the recorder/player according to thepresent invention is to be installed may be a portable recorder/playersuch as a notebook personal computer and PDA (portable digitalassistant), a stationary recorder/player such as a desk-top personalcomputer and server, an in-vehicle recorder/player or the like.

Also note that the dimensions referred to herein concerning therecorder/player according to the present invention are just examples andthe present invention may be constructed with any other appropriatedimensions.

1. A recording and/playback apparatus comprising: an optical pickup unithaving an objective lens disposed therein; a pickup moving mechanism tomove the optical pickup unit; and an engagement member which engages anpickup base of the optical pickup unit and the pickup moving mechanismwith each other, the engagement member including: an engagementprojection engaged in threads formed on a lead screw; and a compartmentprovided contiguously to the pickup base to house a clearance definitionmember which retains the engagement projection at a distance whichassures the engagement on the lead screw, the clearance definitionmember being housed in isolation from the wall of the compartment by aclearance smaller than the depth of engagement of the engagementprojection with the threads on the lead screw.
 2. The apparatus as setforth in claim 1, wherein the pickup moving mechanism includes a stepmotor which drives to rotate the lead screw.
 3. A recording and/orplayback apparatus comprising: an optical pickup unit including a pickupbase; a pickup moving mechanism including a lead screw which moves thepickup base; and an engagement member including: a side wall fixed tothe pickup base and having formed outside thereof an engagementprojection engaged on the lead screw; a compartment having housedtherein a clearance definition member which supports the inner surfaceof the side wall to maintain a distance that assures the engagementbetween the engagement projection and lead screw; and a hinge providedon the base end of the side wall and flexible in a direction in whichthe side wall is moved toward or away from the lead screw, the clearancedefinition member including a support piece extending along the innersurface of the side wall toward outside the compartment.
 4. Theapparatus as set forth in claim 3, wherein the support piece is bentoutside the side wall.
 5. The apparatus as set forth in claim 3, whereinthe clearance definition member being housed in isolation from the wallof the compartment by a clearance smaller than the depth of engagementof the engagement projection in the threads on the lead screw.
 6. Theapparatus as set forth in claim 3, wherein the compartment has anopening formed in the bottom thereof.